Nine years ago Wednesday, President Obama declared his campaign for the White House -- nine years of acrimony and vitriol, nine years of relentless Republican opposition, nine years in which it has often seemed that Congress couldn't so much as name a post office without a filibuster.

Still, Obama says, those nine years have not diminished his faith in the American political system, his faith in negotiation, in dealmaking and in the give and take of  democracy. The president articulated that faith again Wednesday in a heartfelt speech at the State Capitol in Springfield, Ill., where he first announced his presidential candidacy nearly a decade ago.

For Obama, the occasion was an opportunity to reflect on his career in public life and to lay out his take on today's politics. He left out the talking points and the applause lines, telling his audience he had more important things to say.

Obama explained at length about the profound shifts in American politics that have made congressional dealmaking all but impossible. He offered remedies: new rules on campaign finance and redistricting, along with an exhortation to revive an old spirit of bipartisanship that now seems  lost to history.

The president campaigned on a promise to overcome the nation's differences, a promise he has not been able to fulfill. Nine years later, in the face of all the evidence, he hasn't given up hope.  Yet research in political science gives reason to doubt the effectiveness of those solutions. By now, the forces driving Americans apart may be beyond our control.

'A life of its own'

In his speech, the president argued that there is more uniting Americans than dividing them, but that the institutional quirks of U.S. elections stand in the way of progress. He suggested that collegiality and civility are the essence of lawmaking and that leadership is the skill of hammering out compromises.

"We can’t move forward if all we do is tear each other down," Obama said, "and the political incentives as they are today too often reward that kind of behavior."

Compromise is becoming more infrequent as Americans' political divisions have intensified, a trend that began decades before Obama spoke at the state house in Springfield in 2007.

As Wonkblog has reported, Americans have become more likely to view members of the other party as selfish and unintelligent. Many see the policies of the opposite party as "so misguided they threaten the nation's well-being," as worded in a survey fielded by the Pew Research Center.

The antipathy is so intense that many Americans say they'd object if their children married outside their party. About one in 20 Americans said they'd be "displeased" with a potential son- or daughter-in-law who belonged to the other party in 1960. The share opposed to bipartisan weddings has increased to one in three Democrats and nearly half of Republicans today.

Overall, in the four decades between 1978 and 2008, Democrats' ratings of Republicans declined by 15 points out of 100, while Republicans' ratings of Democrats declined by 10 points.

It is a "fundamentally different era" for American politics, Emory University's Alan Abramowitz told Wonkblog last year.

He and other political scientists are still working to understand what caused this shift, but race seems to have been an important factor. There used to be conservative voters and politicians in both parties, but when President John Kennedy -- a Democrat -- took a stance in favor of civil rights in 1963, conservative Democrats began to abandon the party.

The Republican position on racial relations likely attracted voters who were also receptive to tough-on-crime and welfare-to-work policies, voters who held traditional opinions on women and the family and voters who were more bellicose in their view of foreign affairs, explained Marc Hetherington, a political scientist at Vanderbilt University.

"As you fit more of these things together for your followers, you start to attract a larger and larger group of people," he said in a recent interview. "It, kind of, takes on a life of its own."

Obama addressed these trends in Springfield. "What’s different today is the nature and the extent of the polarization," he said, according to a transcript of his remarks from the White House. "A great sorting has taken place that drove Southern conservatives out of the Democratic Party, Northern moderates out of the Republican Party, so you don’t have within each party as much diversity of views."

The ultimate result was two parties composed almost entirely of people who saw the world similarly -- two parties increasingly incapable of talking to each other. More and more, Democrats and Republicans just couldn't see eye to eye, and they lost interest in hearing what the other side had to say. Mistrust festered.

'A lot in common'

Whatever is driving the parties apart, the implications for lawmaking are clearly serious. Obama's speech was a paean to the legislative process, a kind of elegy for a forgotten bipartisanship.

"Despite our surface differences -- Democrats and Republicans, downstate hog farmers, inner-city African Americans, suburban businesspeople, Latinos from Pilsen or Little Village -- despite those differences, we actually had a lot in common," Obama said, fondly recalling his days as an Illinois state legislator.

"We cared about our communities. We cared about our families," the president said. "We cared about America." He described working across the aisle in Springfield to make several bipartisan initiatives into law.

"Democrats and Republicans and independents, and good people of every ethnicity and every faith, shared certain bedrock values," Obama said.

As voters have polarized, the disagreements among American legislators have sharpened. More and more votes are cast on party lines, political scientists have found. Republicans, in particular, have become more ideologically committed.

In short, Americans are bitterly divided on a range of issues, and their legislators are faithfully representing their constituents.

In his speech, Obama mistakenly shifted the blame away from those constituents. He argued that money in politics was distorting the political process. In fact, the available political science suggests that whatever other ills money brings to politics, it also moderates candidates in both parties, making compromise more likely.

In the current campaign, for example, candidates whose extreme rhetoric Obama implicitly criticized in his speech are receiving less money from wealthy donors. Data from the Federal Election Commission show that 85 percent of donations to Democratic Sen. Bernie Sanders's campaign last year were in amounts of less than $200, compared with just 25 percent of donations to rival Hillary Clinton's campaign.

Among the Republicans, Sen. Ted Cruz and Ben Carson respectively received 56 percent and 74 percent of their donations in amounts of less than $200. Sen. Marco Rubio received 25 percent, and Jeb Bush received 6 percent.

These figures understate the reliance of politicians such as Cruz, a senator from Texas, on wealthy contributors, since they do not include the millions donated to political action committees independently supporting him. Proponents of campaign finance reform argue that the system could be designed to limit the influence of concentrated wealth without buying a soapbox for the most extreme voices.

All the same, it is difficult to see how the erosion of the middle ground that Obama described in Springfield can be attributed mostly to money in politics.

Moving apart

It is not the wealthy donors who fund American elections who have become more divided, but Americans themselves. Indeed, Americans have moved apart geographically as well as politically. Many live in towns and neighborhoods inhabited largely by the like-minded.

Maybe it's that liberals are only renting apartments above yoga studios. Maybe it's that conservatives are only buying houses surrounded by enough land that they can shoot gophers off the back porch.

Whatever the reason, more and more Americans live in places where they are unlikely to encounter someone who disagrees with them, according to recent research by James Thomson and Jesse Sussell of the RAND Corporation, the nonpartisan research group.

That trend points to a flaw in another of Obama's arguments: that gerrymandering has forced candidates to adopt extreme views.

The president pointed out that one of the two parties now firmly controls many congressional districts. "If you’re a Republican, all you’re worried about is what somebody to your right is saying about you, because you know you’re not going to lose a general election," he said. "Same is true for a lot of Democrats. So our debates move away from the middle."

To be sure, candidates who live in districts where the main competition is in the primary have more reason to take extreme stances. Gerrymandering, however, is not the reason that larger majorities of voters in so many districts belong to one party or the other, Thomson and Sussell found.

Like-minded voters were no more clustered at the level of the congressional district than at the level of the county, according to their analysis. In other words, the process of drawing boundaries did not make districts more segregated by party than individual communities already were. Americans gerrymandered themselves.

Obama's former budget chief, Peter Orszag, is among those who argue that gerrymandering has not caused polarization.

"The era of gridlock government is unlikely to disappear overnight," Orszag wrote in 2011 in a column on gerrymandering. "We might as well figure out how to function with it."

In many ways, Obama has. During the Obama administration, Congress has created powerful agencies over which it has limited its own authority, such as the Independent Payment Advisory Board for Medicare and the Consumer Financial Protection Bureau. Those bodies are largely unaffected by legislative dysfunction.

In his second term, Obama has also relied extensively on executive authority, independent of the legislative branch -- although the courts have prevented him from carrying through his policies on deportation and power plant emissions.

Looking ahead, several of those candidates vying to replace Obama are wholly rejecting his doctrine of the middle ground. In particular, Sanders, the senator from Vermont, argues that only a "political revolution" will make progress possible again.

The tone of the campaign is not one of compromise. In practice, Obama has been forced to give up on negotiation, too.

Still, he hasn't let go of the vision the animated him nine years ago, when he was still a young senator and an unlikely candidate for the Democratic nomination -- the vision that captivated not only him, but his audiences all around the country.

In Springfield Tuesday, he called it "the vision I shared when I said we are more than just a collection of red states and blue states, but we are the United States of America."

He was paraphrasing a line he first delivered in his famous speech at the Democratic National Convention in 2004 in Boston. That line is even less true today.