In this edition: The 2020 presidential primary season gets underway, the left debates Warren vs. Sanders and anti-Pelosi Democrats hear some primary-challenge noise.

Welcome to 2019, the year of The Trailer.

At 8:43 a.m. on the final day of 2018, Sen. Elizabeth Warren tweeted that she was exploring a bid for president. By 10 a.m., we saw what she was in for. A CNN analysis called her a "below par" candidate; Breitbart labeled her "Pocahontas" in a headline; and the editor of the socialist magazine Jacobin predicted that Warren would lose her own state in a primary.

More than most potential candidates for the president, Warren seemed to be ready for the brickbats. The senator from Massachusetts is the first high-profile Democratic contender, with preexisting grass-roots support, a national fundraising network and credible poll numbers in early-voting states. Four years ago, Warren rejected a campaign to draft her into the presidential primary; since then, she has grown more influential in the party, introducing bills that would give workers more control of corporations, shrink the influence of lobbyists and turn the federal government into a generic-drug manufacturer.

Warren's also the first 2020 contender with a serious army of political enemies, most of them on the right, who have spent much of the past decade trying to stop her rise. It's not easy to be Rep. John Delaney (D-Md.), who has toiled to raise awareness of his presidential campaign since July 2017. But he's been able to do so without Republicans sending trackers, filing requests for public information and asking for ethics investigations. Warren's most controversial decision of 2018 — to take a DNA test and release the results — was spurred by six years of questions about why she once identified as Native American. 

Warren's announcement can be fairly seen as the start of the 2020 Democratic primary. The question for Democratic voters is whom to nominate; the question for the press is whether we've learned anything from a 2016 campaign that made fools out of many experts. Plenty of first-look commentary on Warren is repeating the mistake that led many to suggest that Donald Trump could not win the 2016 Republican nomination, or that Sen. Bernie Sanders (I-Vt.) would be, at best, a token challenger for Hillary Clinton.

So, we don't know who's going to win this thing. But we have a better idea of what is and isn't going to matter when Democrats start piling in.

First, the party in power is not great at guessing whom it should run against. It's an open secret that Republicans consider Warren to be the weakest top-tier Democratic candidate. The arguments for that run from the sensible (President Trump has defined her effectively as "Pocahontas") to the fanciful (she's a female baby boomer and Trump already beat one of those). Early polling backs some of this up; Quinnipiac's pre-Christmas survey found that 37 percent of voters already viewed Warren negatively, more than any other Democrat.

That would be compelling if not for two small details: Barack Obama and Donald Trump. Both entered their primaries as underdogs seen by the other party's front-runners as beatable. In Trump's case, Democrats were literally rooting for him to succeed; a memo published after the hack of Clinton campaign emails revealed that the Democratic front-runner wanted far-right candidates such as Trump to serve as "Pied Pipers," serenading the rest of their party off a cliff.

"We need to be elevating the Pied Piper candidates so that they are leaders of the pack and tell the press to [take] them seriously," the campaign wrote. 

That email was sent in April 2015. One month later, a Quinnipiac poll showed Clinton leading Trump by 18 points.

Second, the "establishment" isn't operating the way it used to. One of the great paradoxes of the last Democratic primary season is that the forces that lost — supporters of Sanders — routed the forces that won. For more than a year, they fought for, and won, changes to the Democratic primary rules that eliminated the voting power of superdelegates on the first ballot at any convention. At the same time, they won commitments from the Democratic National Committee that set up earlier debates and prioritized candidates with "grassroots fundraising." The rules that infuriated Sanders supporters in 2016, allowing Clinton to build a huge delegate lead before facing her opponents, have been overturned.

But the party is not behaving the way it did in 2016. By this point in the previous cycle, 63 Democratic members of Congress had already endorsed Clinton, who was months away from announcing her campaign. As of right now, no Democratic member of Congress has endorsed a potential presidential candidate. The idea of candidates jumping in to prevent a rallying effect for someone else is, for now, defunct, and the results in 2016 (such as Sanders's landslide win in New Hampshire) cut against the idea that endorsements from prominent Democrats can move votes.

What don't we know? Well, for the first time since 2004, Democrats have a wide-open primary field with no "establishment" favorite, and not much of an establishment to decide on one. The 2008 and 2016 primaries eventually settled into battles between Clinton, representing the old party leadership, and a candidate who could define himself as a change agent. Some Democrats see Joe Biden potentially filling that establishment role, but none see him consolidating party support the way Clinton did. 

Third, the two parties' voters are different. The most interesting aspect of Warren's launch video was how it diverged from the messaging of every recent Democratic nominee for president. In 2016, Republicans got behind a candidate who argued that there was no compromise with the political class and that a strong leader was needed to dismantle it. Democrats have generally argued that good people can differ and unite against the minority of special interests keeping the government from answering voters' needs. 

"What's stopped us is the failure of leadership, the smallness of our politics — the ease with which we're distracted by the petty and trivial, our chronic avoidance of tough decisions, our preference for scoring cheap political points instead of rolling up our sleeves and building a working consensus to tackle big problems," Obama said in the first speech of his 2008 campaign.

Warren's first message to voters is different, identifying the economic anxieties of voters and then immediately assigning blame. "These aren’t cracks families are falling into — they’re traps," she says in her launch video. "America’s middle class is under attack. How did we get here? Billionaires and big corporations decided they wanted more of the pie. And they enlisted politicians to cut them a bigger slice."

Like Sanders, who may end up joining the race, Warren simply does not use the language of compromise or national unity; she uses the language of resistance. As they pile into the race, some Democrats will find themselves arguing for a return to the less divisive politics of the pre-Trump era, while others, such as Warren, will call for a president to dismantle the financial forces that made Trump's win possible. To those in the latter camp, Trump never could have won had he not been able to define himself as a "blue-collar billionaire" against Clinton's Wall Street supporters; for them, in 2020, the job will be giving him an opponent who can make a populist case against him. 

What we don't know is how much Democratic voters crave that. For a very long time, Democratic voters told pollsters that they wanted leaders who could compromise with the other party. From 2017 to 2018, according to Pew Research, the proportion of Democrats saying that fell from 69 percent to 46 percent.

That's still a substantial bloc of voters, and in interviews with Iowa Democrats last month, The Post found plenty of them worrying that a "divisive" candidate could not win the presidency. The forces that ended up giving the Republican nomination to Trump do not exist on the left. What is motivating Democratic voters? Thanks to Warren, we'll find out pretty soon.

WHAT I'M WATCHING

What will the left do? There has been a clamor for Elizabeth Warren to run for president since the day she arrived in the Senate. Now that she's in, some of the first notes of skepticism came from people who had pined for her to do this four years ago. The reason: The left found a champion in 2016, and few people who consider themselves part of the left want to see Warren face off against Bernie Sanders.

"If Bernie does or doesn't get in, my concern is whether the progressive vote splits up and we have the same kind of nominee we had last time," said one early-state operative who was still deciding which candidate to work for. "It would be great to have one strong, progressive voice. It's not going to happen."

There's plenty of overlap between Warren and Sanders on policy, and both are likely to get rounded into one of the press's "lanes" or "tiers" as the left's potential candidate. But one of the most interesting debates inside the Democratic Party right now is between Sanders's democratic socialism and Warren's reformed progressivism. By doing so well in 2016, Sanders exploded the popularity of a political philosophy that had been sidelined in the United States for 100 years; Warren hasn't had the same platform to spell out what she stands for.

One of the best elucidations of the two politicians' differences came last year from David Dayen, who's set to become the editor of the liberal magazine the American Prospect. Warren, wrote Dayen, "wants to make capitalism work for everyone," while Sanders does not think it can.

"You can restructure markets so everyone benefits, or you can break down the market system, either eliminating the profit motive or giving everybody a public option," Dayen wrote. "The impulse is the same: The game is rigged and must be fixed. But there’s a long gap between re-writing the rules of the game, as Warren wants, and turning over all the chess pieces, as Sanders does."

Jacobin founder Bhaskar Sunkara, who (as noted above) was skeptical that Warren could win her state's primary, has warned that socialists can't depend on her to deliver systemic change. Sanders's politics grew out of the fading socialist movement; Warren's grew out of research into bankruptcy.

"She'll have the problems Sanders had early on in 2015, and I don't see her catching fire," Sunkara said.

DEMS IN DISARRAY

Democrats now expect Rep. Nancy Pelosi to become the next speaker of the House after she put down several small rebellions by centrists. But at least one House Democrat is already facing a primary challenge over her refusal to back Pelosi (D-Calif.), and at least nine more are being looked over by left-wing groups that want to continue moving the party in their direction.

New York activist Siela Bynoe is considering a challenge to Rep. Kathleen Rice (D-N.Y.), one of Pelosi's most persistent critics, and her supporters are circulating a poll that suggested the Pelosi issue could make Rice vulnerable. While Rice's personal approval rating in her Long Island district was 70 percent — higher than Pelosi's — the pollster found a slight majority of Democrats open to opposing Rice once informed that she opposed the Democratic leader.

"Kathleen Rice has fatally misjudged Democrats in her district," said Evan Roth Smith of Slingshot Strategies, which conducted the poll. "Sixty-five percent of primary voters want to see unity among Democrats, and less than half say they're likely to vote for Rice again after her opposition to Pelosi. Rice may think she's taking a principled stand, but primary voters see it as craven political grandstanding and are punishing her accordingly."

Rice's 4th District is not quite as blue as the typical Democratic primary battlefield. Republican candidates for president regularly win around 44 percent of its vote, more than double their support in Rep.-elect Alexandria Ocasio-Cortez's 14th District. But Sean McElwee of Data for Progress is conducting polls in 10 districts, a mixture of places where moderate incumbent Democrats represent much more liberal electorates and places where certain votes or issues could create an opening for a challenger.

2020

Bernie Sanders. Dozens of veterans from his 2016 campaign are seeking a meeting on sexual harassment policy — a meeting that broke into public view thanks to Alex Thompson at Politico.

Michael Bloomberg. The billionaire said on "Meet the Press" that he'll make a decision on a 2020 run in January or February and that any serious candidate needs to focus on climate change.

Terry McAuliffe. The former Virginia governor told CNN that he is “obviously looking” at a presidential bid, then distinguished his support for universal health care from the versions endorsed by liberal Democratic senators: “We have to actually pay for what we're actually promising.”

Elizabeth Warren. She's en route to Iowa for the first time in years, barring any complications with the Senate's schedule. A tentative itinerary reviewed by The Post has her in Council Bluffs, Sioux City, Storm Lake and Des Moines.

READING LIST

"How Elizabeth Warren is courting black voters and their leaders," by Annie Linskey

Can a candidate like Warren break through in a race with a credible, female black candidate? She's finding out.

“2019: The Year of the Democrat? Think Again,” by Patrick J. Buchanan

He doesn’t exactly have the president’s ear, but Buchanan’s political thinking neatly lines up with Trump’s. Here he makes an argument you might hear a lot of on the right — that the growing diversity of the Democratic Party’s coalition will weaken it ahead of 2020.

“The 2020 book primary is on,” by David Siders

A funny (or at least “laugh so you don’t cry”) look at the unmemorable memoirs that Democrats are going to force every reporter to read ahead of the primaries.

COUNTDOWN

... two days until the 116th Congress is sworn in
... 750 days until the next presidential inauguration