WASHINGTON — A gnawing question is coursing through the Democratic Party as its nearly two-dozen candidates crisscross the country: Whether the party’s top goal of defeating Donald Trump is helped or hindered by the forces pulling Democrats this year in a diverse, future-oriented and unabashedly liberal direction.

Joe Biden’s entrance into the race this week thrust that friction to the forefront, as the former vice president issued a call to arms in a “battle for the soul of this nation.” He was referring to the fight coming in November of 2020 but he could have been talking about the battle being waged with similar vigor for the soul of the Democratic Party.

Remove Trump from the picture, and the case for a Biden candidacy becomes slimmer: At 76 and with nearly half a century in Washington under his belt, he is an imperfect fit for voters who feel disillusioned by politics-as-usual and aspire to prove that leadership is not reserved for those who are older, white and male — particularly with the party still bruised the defeat of establishment-favorite Hillary Clinton in 2016.

Their candidates’ biographies aside, Democratic primary voters have been animated this year and in the 2018 midterms by appeals to progressive purity, rejection of corporate influence on elections and the embrace of far-left policy proposals such as reparations for slavery, voting rights for felons and free college. Those kinds of policies could put the eventual Democratic nominee, if he or she embraces them, at a disadvantage in the general election.

Some party veterans are gearing up to make the case to Democratic voters that a nominee too far left will hand Trump a second term.

“There will be a big debate over whether an experienced elected official or a figure of generational change will be best to take on Donald Trump,” said Ben LaBolt, who worked for former President Obama’s campaign and followed him to the White House. At the same time, he said: “We can’t set up litmus tests that take our eye off the prize.”

The push within the party for presidential candidates to reject money from lobbyists and bundlers, for example, will not stop Trump from gladly accepting those dollars, LaBolt said — and using them against the Democratic nominee.

“If we want to reform the system then we should win the election and reform it,” he said. “I don’t think we should put significant additional constraints on ourselves while the process is playing out.”

Other Democratic veterans of past elections said they plan to make the case to rank-and-file voters that if the nomination goes to one of the more-progressive candidates — like Sens. Bernie Sanders, I-Vt., Elizabeth Warren, D-Mass., Kamala Harris, D-Calif. or Cory Booker, D-N.J. — the prospects of beating Trump fizzle.

“If it’s Bernie or Elizabeth, we’ve got trouble,” said former Pennsylvania Gov. Ed Rendell, who is supporting Biden in the primary. Harris or Booker, he added, also could provide “fertile ground” for Trump to effectively characterize 2020 as a choice between re-electing him and turning America into a socialist country, which could alienate some key voters in states like Pennsylvania, Wisconsin and Ohio.

“Hopefully the moderate-center of the party understands,” he said. “And it’s the job of people like me to keep explaining it.”

Others in the party are taking it on themselves to make the opposite argument — particularly to millennial voters and those who believe catering to the perceived proclivities of “moderate” voters is the reason the party lost the last election.

Waleed Shahid, a former staffer for Rep. Alexandria Ocasio-Cortez who runs the group Justice Democrats, said Friday on MSNBC that Biden lacks support from core Democratic constituencies who failed to turn out in high numbers in 2016, including voters who are young, female, black and union members.

“On issue after issue, Joe Biden has chosen the wrong side of history on where the Democratic Party is going,” Shahid said.

So then why, if the base of the party seems to be pining for something fresh, does poll after poll show the early race dominated by Biden and Sen. Bernie Sanders, two white men in their late 70s?

Celinda Lake, a Democratic pollster, said the number of Democrats who say their top priority is electability or defeating Trump is at “record highs,” at 38 percent to 41 percent in recent polling.

“It beats everything else. It beats values by 3-to-1. It beats character by 10 points,” Lake said. “We’ve never had it that high before.”

There’s another difference this year: Traditionally, voters tend to think that whichever candidate they like also happens to be the most electable. In 2016, Clinton’s supporters were convinced she had the best chance, while Sanders’ backers felt the same about him.

Not this year, Lake said.

“For the first time, this year it’s really an independent assessment. People don’t necessarily think the person they’re intrigued with at the moment is the most viable, and they’re really trying to sort it out,” she said. “It makes the race much more fluid.”

But Shahid, in a later interview, said there’s a critical factor beyond which Democratic candidate is most likely to convert voters in the general election who may have backed Trump last time: If the Democratic base isn’t enthused about their nominee, they may just stay home.

“I think Joe Biden thinks electability is about moderation,” Shahid said. “But electability is also about motivation.”

The push-and-pull between a narrow focus on countering Trump at the ballot box versus embracing a bolder political vision — is also playing out as the Democratic Party navigates other charged issues in the nearer term.

In Congress, while many are eager to launch impeachment proceedings, Democratic leaders have been working to keep that at bay, wary of alienating Republicans and independents in a move that could be counterproductive for next year’s elections. A similar dynamic is on display as Democrats wrestle with how far to lean on policy issues like the Green New Deal, an environmental and economic proposal that would be easy for Trump and Republicans to deride as “socialist.”

Biden, as he launched his campaign, staked his candidacy on stopping Trump from winning a second term that he warned would “forever and fundamentally alter the character of this nation.” Yet some Democrats took note that there was little mention about what he would do affirmatively with his years in the Oval Office, other than undo the previous four.

“I think it’s going to take more than just telling people that we want to take things back to the pre-Trump era. Because at this point we can’t really do that,” said David Reid, a lobbyist and former Hillary Clinton fundraiser who is supporting South Bend, Ind., Mayor Pete Buttigieg. “It’s going to take a more creative and novel approach to take us out of this and help us to repair the damage.”