Early in the year, the party's liberal wing seemed to be ascendant, defined by the candidacies of Sens. Bernie Sanders, I-Vt., and Elizabeth Warren, D-Mass., and the embrace of a single-payer, Medicare-for-all health-care program. Sanders and Warren were calling for other dramatic changes to the system - economic and political - and their voices stood out. Some other candidates offered echoes of their ideas.
That proved to be a misleading indicator of where the Democratic electorate was on some of the issues, particularly health care, in part because there were fewer moderate voices being heard. Former Vice President Joe Biden didn't join the race until April. South Bend, Indiana, Mayor Pete Buttigieg wasn't being taken very seriously. Sen. Amy Klobuchar, D-Minn., wasn't breaking through.
The candidate debates provided the setting for the arguments to play out before a larger audience. Warren and Sanders came under attack from moderate Democrats at the first debate in June in Miami, with former Maryland congressman John Delaney the most vocal. But Warren and Sanders more than held their own. It appeared as though the progressive wing was on solid ground.
Subsequent debates, however, have produced a different impression. The progressives have been much more on the defensive and the moderates more assertive. Biden tangled with Sen. Kamala Harris, D-Calif., in the Detroit debate over the issue of health care. Harris subsequently modified her position, moving toward the center. On the issue of Medicare-for-all, the ground has shifted.
During the Atlanta debate in late November, even Sanders seemed to be tempering his overall message. Asked about comments by former President Barack Obama, who had earlier told some wealthy Democratic donors that the country wasn't looking for a revolution, Sanders replied, "He's right. We don't have to tear down the system, but we do have to do what the American people want."
Judged by the current polling in the four early states, the more moderate candidates are prospering. To the surprise of many, Buttigieg is at the top of the field in both Iowa and New Hampshire, according to the Real Clear Politics average of polls. No one would have predicted that last spring.
Biden trails Buttigieg, Sanders and Warren in those two states, which is hardly a comfortable place to be for someone who was the acknowledged leader in the race when he announced his candidacy and who continues to lead in national polling. But he is ahead in Nevada and he has a big lead in South Carolina, where strong support from African American voters gives him what he hopes will be a firewall in the event that he gets swamped in Iowa and New Hampshire.
The possibility that the four early states could be won by three or even four different candidates is one big reason Mike Bloomberg, the billionaire former mayor of New York, sees an opening for a campaign that skips those four and starts in the states that comprise Super Tuesday in early March.
Is it a coincidence that the more moderate candidates are doing well in those four early states at a time when Obama was sounding his words of caution? Perhaps. But Obama's warnings about going too far to the left provided some context to the race from the perspective of someone who happens to be the first Democratic president since Franklin D. Roosevelt to win more than 50% of the national vote in both of his elections.
What continues to define the Democratic race is the absence of a candidate who has truly captured the imaginations of voters. Buttigieg may have come closest, at least among the voters in predominantly white Iowa and New Hampshire. His talent and intellect have certainly generated enthusiasm, marked by sizable crowds as he has campaigned in those states. But he still faces big questions about whether he can expand his appeal, particularly in the African American community.
Sanders has changed hardly a word from his stump speeches of the 2016 campaign, but in response to criticism, he has been trying to show a more personal side. He has loyal supporters - and truly loyal contributors - but he hasn't truly sparked the grass-roots movement he talks about. With many more candidates to choose from, some of his supporters from the last campaign have gone elsewhere.
Warren entered with sizable name recognition but saw her campaign questioned early in the year as she struggled to gain support. Then she became the star of the field, the candidate with detailed plans and a well-regarded field organization in the states, during the late summer and early fall. That was at a time when Harris was falling back while Klobuchar and Sen. Cory Booker, D-N.J., were still in single digits.
Then Warren hit turbulence over health care and fears that her advocacy for a government-run, system would make it difficult for her to win a general election on that platform. That's where she is today. Having overcome doubts at the beginning of the year, she will have to do it again at the end of the year.
Biden has been Biden. He can be underwhelming at times, steady at others. But he still lacks the kind of message that Obama, no doubt, would want to see in a challenger to President Donald Trump. The attributes that have kept him generally atop the national polls are that he is familiar, experienced, well liked in the party and still seen by many Democrats as the candidate with the best chance of winning in 2020. Despite that, he gets little praise from the commentator class on cable television.
Biden's advisers would say he is closer on issues to the Democratic primary electorate than he's given credit for and that his appeal to African Americans (particularly older black voters) and to white working-class voters makes him well positioned for a run against Trump. But talk to party strategists in a state like Iowa and the first thing they say about Biden is that he's generated little enthusiasm as a candidate.
Two months of campaigning remain before the first votes are cast on Feb. 3 in Iowa. In December, impeachment proceedings in the House will overshadow what the candidates do and say; then the holidays will offer voters a possible timeout from everything political.
In January, an impeachment trial in the Senate could tie up the senators in the race - Sanders, Warren, Klobuchar, Harris, Booker and Michael Bennet of Colorado - but notably not Biden or Buttigieg. Whether that gives the non-senators an edge in the weeks when many voters will be making their decisions is the question.
More than in some past campaigns, Democratic voters appear torn between heart and head. Many are looking for a candidate who will inspire them while also being somewhat risk-averse. Those conflicting impulses could be one reason the race seems to shift and shift again and why the answer to the question of what and who it will take to beat Trump still lies at the center of it all.