The 2020 presidential campaign began more than a year ago, and it has been a whirlwind of Democratic town halls, kaffeeklatsches, candidate debates, fundraising appeals, Twitter spats and nonstop punditry — all competing for attention against the overriding presence of President Trump. What still lies ahead could be a political season like none other.

After all the 2019 preliminaries, voters will finally begin to speak in Iowa on Monday night at that state’s precinct caucuses. New Hampshire’s primary will come eight days later, followed in February by caucuses in Nevada and a primary in South Carolina.

From there, the contest for the Democratic nomination will immediately fan out across the country in a rapid series of primaries and caucuses that could make clear by the end of March the identity of the likely Democratic nominee — or foreshadow a potentially wrenching fight among two or more candidates all the way to July’s national convention in Milwaukee.

Whenever the Democrats finally settle on their nominee, that person will enter a general-election contest that Trump and his reelection campaign have been waging almost from the time the president took the oath of office three years ago. The Trump machine is likely to be the best-funded in history and, by the assessment of some Democratic strategists, might be the most sophisticated presidential campaign operation they have encountered.

The Nov. 3 general election is seen by many voters, regardless of their party allegiance or ideology, as the most important in their lifetimes. Trump’s presidency has been one of controversy and division from the very beginning, one that has further polarized an already divided country.

All reelection campaigns are judgments on the incumbent, but this year’s stands as one in which strong passions about the president, pro and con, and assessments of what his presidency means for the future override almost everything else — the economy being one wild card — in determining how people will vote.

Campaign 2020 is unique in many ways: the number of candidates who have sought the Democratic nomination; the increasing reliance on small-dollar donations from grass-roots activists; a primary calendar that gives no pause for candidates until the end of March; a general election that could have fewer true battlegrounds than ever. What makes this year different, Democratic media strategist Jim Margolis said, is that “everything is on amphetamines.”

The year also will mark the first time in the nation’s history that an impeached president will be seeking reelection, assuming the Senate acquits Trump at the end of the trial now underway. Twice before, presidents have been impeached but not convicted: Andrew Johnson in 1868 and Bill Clinton in 1998. Neither was on the presidential ballot in the subsequent general election. Trump will be the first to try to convert the stain of impeachment into a political asset to win a second term.

Democrats hope that the desire to drive Trump from office will become the salve that repairs any lingering wounds after their nomination contest. Right now, however, there is little time to ponder that, as the candidates and campaigns are almost singularly focused on one another and on winning the nomination.

The early states

Iowa and New Hampshire kick off the year amid recurring controversy over the role those two small and predominantly white states play in the selection of presidential nominees. That debate will continue well beyond this election year. For now, the candidates know that the calendar is fixed and that the results Monday in Iowa and Feb. 11 in New Hampshire will shape everything going forward.

The last four Democratic winners of the Iowa caucuses — Al Gore in 2000, John F. Kerry in 2004, Barack Obama in 2008 and Hillary Clinton in 2016 — all went on to win the nomination. Since 1976, there have been only two cases when the Democrat who led at the caucuses did not become the Democratic nominee, the last occurring in 1992 when no one competed against favorite-son Tom Harkin. That is why the record-large field of Democratic candidates has spent so much time, money and organizing effort focused on turning out what will be a fraction of Iowa’s population.

The biggest turnout for the Democratic caucuses in Iowa was 240,000 in 2008, when Obama and Clinton (and others) waged an epic battle. Many Democratic strategists believe this year’s turnout will eclipse that record. They base that assumption on the number of well-organized campaigns actively working to get people out on caucus night as well as the perceptible enthusiasm and energy among Democrats, who turned out in big numbers in the 2018 midterm elections and have swamped presidential candidate events since early 2019.

New Hampshire’s role is equally important. Since the start of the modern primary in 1952, only three candidates of either party have lost the New Hampshire contest and gone on to win the presidency that same year: Bill Clinton in 1992, George W. Bush in 2000 and Obama in 2008.

William M. Gardner, the longtime secretary of state and the guardian of New Hampshire’s first-in-the-nation primary status, noted that the election there is about more than winning: A weak finish can be crippling. No candidate of either party who has finished below second in New Hampshire has won the presidency that year. And since 1972, no candidate of either party has finished lower than second and ended up as the nominee.

Today there are at least four Democrats who believe they could finish in one of the top two slots in both states. Former vice president Joe Biden, who finished far behind Obama and Clinton in Iowa in 2008, is one. The others are Sen. Bernie Sanders (I-Vt.), who narrowly lost to Clinton in Iowa in 2016 and who ran away with the New Hampshire primary the following week; Sen. Elizabeth Warren (D-Mass.); and former South Bend, Ind., mayor Pete Buttigieg.

The Washington Post’s average of state polls shows Biden and Sanders virtually tied in Iowa and Sanders leading Biden and the others by a few points in New Hampshire.

In Iowa, each of the four top candidates has led in one or another version of the highly regarded Iowa Poll, conducted by J. Ann Selzer for CNN, the Des Moines Register and Mediacom over the past half-year. The final Iowa Poll will be released Saturday night.

Biden, Sanders, Warren and Buttigieg aren’t the only ones working to gain a foothold in Iowa. Sen. Amy Klobuchar (D-Minn.) is looking for a surprise finish to give her candidacy the jolt it needs to go forward. Andrew Yang, the entrepreneur turned candidate, has been stumping the state this month with his own hopes riding on what happens. Investor Tom Steyer is campaigning hard on the issue of climate change. Former congressman John Delaney of Maryland has spent more time in Iowa than other candidates, so far to little impact with voters.

Iowa’s caucus rules can skew the support that candidates end up with on caucus night. Candidates who do not reach a 15 percent threshold of support in any precinct get nothing to show for it, their backers freed to shift their votes to someone else.

The result reported by the Iowa Democratic Party reflects that realignment. In the vernacular of Iowa Democrats, the final results will be percentages of “state delegate equivalents,” or SDEs.

But the state party also plans to report two other numbers: the percentage of supporters who show up for each candidate and the percentage of supporters for each candidate after the final vote.

The three-part reporting raises the prospect of a free-for-all in which multiple candidates seek to gain ground by seizing on whichever numbers give them the best talking points.

New Hampshire’s rules are straightforward: The candidate with the most votes wins. But the state’s substantial cadre of independent voters is free to participate in the Democratic primary, and the makeup of the electorate will be influenced by how many do so.

Tad Devine, a Democratic strategist who worked for Sanders in 2016 and now is working for Yang, predicted that Sanders victories in the first two states would open an intraparty battle. “If he wins Iowa and New Hampshire, the lines are going to be drawn between the progressive wing and the establishment,” Devine said.

The votes by Nevada Democrats on Feb. 22, and by South Carolina Democrats on Feb. 29, will mark the first time nonwhite voters will play substantial roles — Latinos in the western state and African Americans in the east. The latter vote will take place only three days before the Super Tuesday contests deliver the single biggest haul of delegates.

“I think South Carolina matters so much more than it ever has,” said Jen O’Malley Dillon, who was campaign manager for former congressman Beto O’Rourke of Texas before he dropped out of the race and who was deputy campaign manager for Obama in 2012. “In part because of this short timeline but also because of the way we’ve built this cycle with the question of who has the support of the Obama coalition. That carries much more weight than it ever has.”

The second wave

Winning the Democratic nomination on the first ballot in Milwaukee will require amassing 1,991 pledged delegates. A second-ballot fight would open the contest to roughly 771 superdelegates — party leaders and elected officials — and the winner would then need a majority of the total pledged and superdelegates, according to Democratic National Committee officials.

The first four states on the calendar account for 155 pledged delegates, or 4 percent of the total that will be selected through June. Super Tuesday on March 3 will see primaries or caucuses in 14 states, including California and Texas, and other locations. On that single day, candidates will be competing for 1,357 delegates, or 34 percent of the 3,979 pledged delegates at stake.

That means beginning March 3, the campaign will shift from its opening stages, when building momentum is the goal, to the period when accumulating delegates claims overriding importance.

Sanders’s goal is to win Iowa, New Hampshire and Nevada, aiming to ride into Super Tuesday as the leading candidate and then to position himself as the front-runner. Faiz Shakir, Sanders’s campaign manager, said that, if they’re successful in the early states, “getting into California and Texas and putting ourselves into position to expand our delegate lead would be crucial.”

Biden’s team has said he can afford to lose Iowa and possibly New Hampshire, and recoup in South Carolina, where he continues to enjoy strong support from black voters. “We knew that the strength of our campaign is the diversity of our support,” said Greg Schultz, Biden’s campaign manager. “No matter what happens in the first two, it’s not until Nevada, South Carolina and Super Tuesday that the country as a whole is represented. We have built our campaign for that.”

Buttigieg’s team knows he must do exceedingly well in Iowa to demonstrate that a young, gay former mayor of a fairly small city can truly be a competitive candidate for the presidency. “We really are counting on the mayor doing well in the first two contests,” said Mike Schmuhl, Buttigieg’s campaign manager, “to show that he can beat other people and to buttress our electability argument and also our change argument, that people are looking for something different.”

Like Biden, Warren has signaled she is looking to play a long game, though she cannot afford to fall far behind in the earliest states. Her campaign is betting that the results in the first four states will be enough of a muddle to set up the March primaries as a possible showdown. “We think Super Tuesday and all the March states as a whole are important,” said Kristen Orthman, Warren’s communications director. “We’ve allocated resources as such basically throughout the year.”

She added that the campaign began building operations in Super Tuesday states many months ago and that Warren has visited every state voting March 3, with the exception of Maine and Vermont, both adjacent to Massachusetts, and Arkansas. “That wasn’t by accident,” she said.

Super Tuesday also will be the first day that Mike Bloomberg, the former New York mayor, will be on ballots. Bloomberg is skipping the first four contests, a strategy no successful candidate has pursued in the modern era. He has already dropped more than a quarter of a billion dollars into television ads and organizing in Super Tuesday states and has the capacity to do what no other candidate can afford to do to reach voters.

But Bloomberg’s hopes of becoming competitive rest almost entirely on whether, after the first four contests, Biden is doing well or gasping for support, and if any other moderate — Buttigieg or Klobuchar, for example — has swept into contention.

“It may be that what we have seen since 1976 largely repeats itself, that these two contests [Iowa and New Hampshire] help pick who will go on and win the nomination,” said Kevin Sheekey, Bloomberg’s campaign manager. “Or this may be a very different kind of year. At least one candidate is running a nominal test of running a national campaign.”

The sprawling nature of the Super Tuesday competition and the lack of time for any campaign besides Bloomberg’s to invest broadly will require candidates to make difficult choices about where they spend time and money. “The whole exercise is targeting resources,” said Robby Mook, who was the 2016 Clinton campaign manager. “You cannot do everything.”

Past years have given candidates some time to regroup after the first primaries and to campaign in the swath of states that follow. Not this year. There are just three days between the last of the initial four elections and the Super Tuesday contests, meaning the winner of South Carolina will have an edge in media coverage.

“A win in South Carolina is the last thing people are going to hear before Super Tuesday,” said Lily Adams, who was communications director for the campaign of Sen. Kamala D. Harris (D-Calif.), who dropped out in December.

The pace doesn’t slowafter Super Tuesday. The next two Tuesdays will account for an additional 23 percent of the delegates available; the surviving candidates will have to run a gantlet of big states like Michigan, Illinois, Florida, Ohio and Arizona. By the end of March 17, 61 percent of the pledged delegates will have been selected.

“March 3 to March 17 is as brutal a thing as we’ve seen in presidential politics, with big states, all the time zones and territories,” said David Plouffe, Obama’s 2008 campaign manager, who helped guide the 2012 reelection from a perch in the White House. “I can’t describe how different running that race is from the race they’re running now.”

The delegate battle

Except in Texas, which apportions party delegates by state Senate district, most delegates are determined proportionally by results in congressional districts, with the remainder awarded to the statewide winner. This arithmetic of allocation means it can be difficult for a candidate to gain a significant advantage — and even more difficult for a trailing candidate to catch up or overtake the leader.

That makes delegate hunting a complex matrix that requires campaigns to know the demographics of every district in the country and how they match up with the appeal of their candidate. Most important, it requires decisions about where it’s worth competing hard and where it isn’t.

Under the party’s proportional rules, some districts award an even number of delegates and others award an odd number. In those with an even number, gaining a split is relatively easy — while winning an advantage requires blowing away the competition. In odd-number districts, a narrow victory can produce an extra delegate.

Moreover, districts where Democrats get their highest percentages in presidential races have extra delegates to award. Many of these have a high proportion of minority voters, especially African Americans. That was a strength for Clinton against Sanders in 2016 and could be valuable to Biden if he holds on to strong support from black Democratic voters.

Insurgent or inspirational candidates, like Obama in 2008 and Sanders in 2016, took advantage of the many caucuses on the calendar to add to their delegate counts. Caucuses tend to draw more energized party activists, even as they disenfranchise voters who are not able to attend at the time they are held. This year, however, the DNC — with the assent of Sanders’s representatives — cut the number of states with caucuses from 14 to seven.

“Every campaign will look at what are their strengths demographically and regionally, and try to put together a profile of where they will do well by state and by congressional district,” said Jeff Berman, who helped craft Obama’s successful delegate strategy in 2008.

Berman added that campaigns must look for opportunities to win states “so their candidate appears on the election night results chart as a winner in multiple states.” Still, the race remains all about winning delegates.

In recent campaigns, the early election night commentary focused on a candidate’s wins in premier states, but when the delegates from all the contests that night were counted, a different picture emerged. One night in 2016, for example, Clinton netted far more delegates from her less-noticed win in Mississippi than Sanders did in his high-profile victory in Michigan.

Several candidates are likely to have the resources to continue their campaigns well into the spring and, potentially, all the way to the July convention. The big question is whether there will be a protracted fight, even if one candidate has a clear, if modest, delegate lead by the end of the March contests.

“After the first four [states] and out of Super Tuesday, I think you’ll begin to see some clarity emerging in the delegate advantage and other advantages,” said Michael Donilon, one of Biden’s senior advisers. “And I think there will be a force that exerts itself, that voters will want to move toward a resolution and not leave this open-ended for a long time.”

Yet even if there is some clarity about a likely nominee there’s no guarantee that the leader will have the 1,991 delegates needed to win on a first ballot wrapped up by the end of the primaries. Would the hundreds of superdelegates who could vote on a second ballot turn to someone other than the delegate leader? That’s a particularly pertinent issue for someone like Sanders, whose possible nomination causes angst among the establishment Democrats who dominate that category.

“That is the path we are trying to avoid,” said his campaign manager, Shakir. “The goal is to win Iowa, New Hampshire, Nevada, sweep into Super Tuesday and crush it. That has dictated every spending decision, resource decision of this campaign.”

Trump and the general election

As Democrats wage their contest, Trump’s campaign will be operating on a separate track, free from any serious challenge for the nomination and focused on the general election. But he will be in the faces of the Democrats at every opportunity, whether through Twitter commentary on his potential rivals or with state-by-state rallies.

He will be on the caucus ballot in Iowa the same night the Democrats hold their caucuses, and he plans a rally in Des Moines on the Thursday before the vote. Another rally is set for Manchester the night before the New Hampshire primary.

Trump has challengers for the nomination — among them former Massachusetts governor Bill Weld and former congressman Joe Walsh of Illinois — but his grip on the Republican Party is so strong that he is free to ignore them. The GOP is helping to assure that; a number of states have either scrapped their primaries or given more control to state party leaders to allocate convention delegates.

Through the end of last year, the Trump campaign and the Republican National Committee raised half a billion dollars, and they began the election year with $200 million in the bank. Collectively, Democrats contributed $1 billion to candidates and organizations through online donations, but whoever becomes the Democratic nominee, with the exception of Bloomberg, is likely to begin the general election cash-strapped by comparison with the president.

Trump’s operation has been building and building, identifying the voters it believes will determine the outcome in November in the states Trump must win to assemble another electoral college majority. “Time is one of the great advantages the president’s reelection campaign has enjoyed, and we have not squandered it,” Tim Murtaugh, the campaign’s communications director, said in an email message.

Murtaugh reiterated that the reelection operation will target not only the swing states Trump won narrowly but other states that Democrats captured four years ago, where the president’s team hopes to put them on the defensive. Pointing to the financial disparity between Trump’s campaign and that of the likely Democratic nominee, he added, “The Democrats will not be able to match the president in resources or organization.”

In many of those states, there has been minimal to no Democratic presence yet. Bloomberg’s hefty advertising campaign is beginning to compensate in some of the most important general-election battlegrounds. The billionaire ex-mayor is setting up field offices in those states and has promised to keep them open until November, even if he isn’t the nominee.

“It has become clearer to me how strong Trump is in the . . . swing states and how much work he has done,” said Bloomberg’s campaign manager, Sheekey. “The more time I spend in Wisconsin or Michigan or North Carolina, the more I realize how difficult those states are going to be to win.”

Trump also will start with the advantage ofa more sophisticated understanding of which voters he needs beyond his core supporters to win a general election. His campaign already is testing various messages on many issues.

The Democratic nominee will start well behind on that front, relying instead on any organic Trump opposition to help narrow the margin. Plouffe recalled that after Obama won the nomination in 2008, and after campaigning in every state, it was like starting over to attract a new set of voters.

“The voters who make the difference don’t know you,” he said. “Yeah, you’ve got staff and volunteers, but you’re not talking to voters who will be front and center in the general election.”

That will be the challenge for whoever becomes the Democratic nominee. But that is at least several months into the future, and only after the biggest field in the history of the Democratic Party is narrowed to the last person standing.