It tells you a lot about state of the Democratic race for president and the lines of division within the party that there are two battles being waged as the campaign for Tuesday’s New Hampshire primary comes to a close.

One is the urgent effort by the party’s moderate and center-left voters to find a candidate who can defeat Sen. Bernie Sanders (I-Vt.). The other is a desperate fight for their allegiance among the candidates vying to become that person. Thus the struggle in the final hours among former South Bend, Ind., mayor Pete Buttigieg, former vice president Joe Biden and Sen. Amy Klobuchar (Minn.). The question is whether they do so much damage to one another that they clear Sanders’s path to victory.

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The wild card is Sen. Elizabeth Warren (Mass.). She rose briefly last fall to a commanding position as the center of gravity in the party between Sanders’s proposed revolution and the party’s incrementalists. But she fell back after she became embroiled in controversy over her evolving position on Medicare-for-all, one of Sanders’s signature issues.

She has made a bit of a comeback by arguing that she is the most plausible unity candidate, but the central drama now is whether Biden and Klobuchar can stop the surge toward Buttigieg. His strong showing in the Iowa caucuses had begun to turn the New Hampshire race into a straight fight between the 38-year-old wunderkind and the 78-year-old democratic socialist.

Biden, fighting for his political life after a fourth-place showing in Iowa, spent the weekend aggressively taking Buttigieg on, arguing that “we’re a party at risk if we nominate someone who’s never held a higher office than mayor of South Bend, Indiana.”

Klobuchar hopes that a commanding debate performance will transform her from an also-ran into a major contender. Trying to seize what may be her last opening, she’s arguing that she can give voters who have rallied to Buttigieg both the moderation they crave and the experience he lacks.

“We have a newcomer in the White House, and look where it got us,” she said in one of her signature lines in Friday’s encounter. “I think having some experience is a good thing.”

Buttigieg thus found himself in a two-front war this weekend. He hit Sanders for offering a choice between “revolution” or “the status quo,” which, he said, would leave “a lot of people with nowhere to go.” And he issued an implicit critique of the Washington veterans at his heels, saying voters from “small- and medium-sized cities like mine” — there are many small communities in New Hampshire — “feel like Washington can’t even hear us.”

The dynamics of the contest were captured well by a tracking poll conducted by the Boston Globe, WBZ-TV in Boston and Suffolk University, which offered clues about the race before and after the debate. It found Klobuchar was the only candidate in the top five who gained ground between the group’s Friday and Saturday surveys, rising from 6 percent to 9 percent. Biden was down a point to 10 percent, and Warren also lost a point, dropping to 13 percent.

The most revealing, although modest shift, was in the Buttigieg-Sanders standings. Pre-debate, Buttigieg led Sanders 25 percent to 24 percent; by Saturday, Sanders was ahead 24 percent to 22 percent. (Another 7 percent was shared by the rest of the field, with 12 percent undecided.)

All this is margin of error stuff, but the closeness and fluidity that the poll reflected is the point. Among them, the three middle-of-the-road candidates — Buttigieg, Biden and Klobuchar — had 41 percent in the survey. This suggests that in a close race, a dynamic toward fracture rather than consolidation will benefit Sanders. His hold on about a quarter of the state’s electorate seems unshakable.

The paradox of the Democratic struggle this year that the splintering within the party’s coalition stands in stark contradiction to the overwhelming sentiment across its rank-and-file for unity against President Trump. Sanders himself underscored the point in Friday’s debate. “No matter who wins this damn thing,” he said, “we’re all going to stand together.”

That may yet prove true. But the story of “this damn thing” up to now is that the faltering Biden campaign has left believers in his Beating-Trump-Is-Everything approach to 2020 split asunder. Biden’s core promise was that he would be the unity candidate who could best draw all the pieces of the Democratic coalition together. Democrats outside the ranks of Sanders’s loyalists are torn because they can’t figure out how to answer the question: If Joe can’t do it, who can?

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