The dynamics of the Democratic presidential race are about to change. Tuesday’s debate in Des Moines will be the grand opening of a new set of conflicts and the launch of renewed efforts by candidates not named Joe Biden or Bernie Sanders to make 2020 something other than a lightly remodeled version of the 2016 primaries.

To say the contest is unsettled is an understatement. Among a series of surveys released since the first day of the year, the most revealing was CBS News’s poll in Iowa: It found former vice president Biden, Sen. Sanders and former South Bend, Ind., mayor Pete Buttigieg all tied at 23 percent, trailed by Sens. Elizabeth Warren (D-Mass.) at 16 percent and Amy Klobuchar (D-Minn.) at 7 percent.

Underscoring the margin-of-error nature of the battle, the respected Des Moines Register/CNN Poll released Friday showed Sanders with 20 percent, Warren at 17 percent, Buttigieg at 16 percent, Biden at 15 percent and Klobuchar at 6 percent. And only 40 percent of those surveyed said their minds were made up.

Why are Democrats so torn about the decision they confront? “The race is unsettled because the voters are unsettled,” said Geoff Garin, a Democratic pollster who is neutral in the contest. “Sanders has a committed base, but otherwise, voters are making intellectual and strategic choices rather than passionate choices. As a result, voters can shift around.”

Thus the high stakes of Tuesday’s encounter, particularly for Warren, Klobuchar and, to only a slightly lesser degree, Buttigieg, whose emergence is the truly fresh story out of 2019.

Polls show that Buttigieg, who turns 38 next Sunday, is in a plausible position to win both Iowa on Feb. 3 and New Hampshire eight days later, an extraordinary achievement for a two-term mayor of a small Midwestern city. But the unlikeliness of his success means he needs victory in at least one of these states, and strong showings in both, to move forward.

This will continue to make him a target of both Warren and Klobuchar, but he must also prevent hemorrhaging some of his votes to fellow moderate Biden. This could lead to a spirited generational conflict between the youngest and second-oldest candidates onstage.

Warren, depending on your point of view, is either stuck between the more moderate candidates and Sanders (and has lost support to both sides) or, as she hopes, now represents her party’s center of gravity and has the best chance to unify it.

Warren as unifier is a new theme, although she was effectively playing that role this fall when she soared to the top of the field by picking up support across the party. This also serves as an answer to those who doubt she can defeat President Trump.

More than anyone, Klobuchar needs to upend the dynamic of the contest. Her survival as the fifth option is not a trivial accomplishment given how many other candidates have already fallen by the wayside. But her candidacy is unlikely to continue past Iowa unless she can cut deeply into Buttigieg’s and Biden’s vote shares. This gives her an interest in provoking dramatic moments on Tuesday while hoping that her two immediate rivals falter.

Sanders, on the upswing, will continue to play his greatest hits for those who never tire of his tune. But the most dovish candidate onstage will likely step up his criticisms of Biden’s foreign policy views, especially his initial support for the Iraq War in 2002. The independent from Vermont is anticipating what is now a strong possibility: Against Biden, he will be the outsider progressive against the insider favorite, a reprise of his breakout role four years ago against Hillary Clinton.

Then there is Biden, so far the great survivor but facing challenges in both Iowa and New Hampshire. “The last year has really not been that interesting,” said Anna Greenberg, a Democratic pollster who worked for former Colorado governor John Hickenlooper’s presidential campaign before he dropped out to run in his state’s U.S. Senate race. “The first half was: Who will pass litmus tests? The second half was: Biden, Biden, Biden and Medicare-for-all.”

Perhaps paradoxically, Greenberg said, the impeachment inquiry and Trump’s attacks on Biden and his son Hunter may have helped the former vice president by keeping him at the center of the conversation and arousing solidarity with him among party loyalists. And Biden’s own debate performances improved enough to reassure Democrats who continue to think he is the party’s best bet against an incumbent they loathe.

Garin, the strategist, argues that there are two kinds of Democratic primary voters: those looking for the strongest progressive to oppose Trump and those looking simply for the strongest Democrat to beat him. Last year started with the accent on the first. As this year begins, the focus — for all the candidates except Sanders — has shifted to the second.

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