Months after Vice President Biden decided against running for president, tensions linger between his camp and Hillary Clinton Hillary Diane Rodham ClintonWhat Senate Republicans have said about election-year Supreme Court vacancies Bipartisan praise pours in after Ginsburg's death Trump carries on with rally, unaware of Ginsburg's death MORE’s campaign and supporters.

Democrats say Biden could be a major figure, along with President Obama, in helping Clinton generate excitement over her Democratic presidential campaign.

ADVERTISEMENT

Clinton’s challenge in the summer and fall will be to unite the party and win over supporters of her rival, Bernie Sanders Bernie SandersKenosha will be a good bellwether in 2020 Biden's fiscal program: What is the likely market impact? McConnell accuses Democrats of sowing division by 'downplaying progress' on election security MORE. Many see Biden, a favorite among Democrats who is popular with white, working-class men, as someone who could be a prominent surrogate on the trail in swing states such as Ohio and Pennsylvania.

“There are only a couple of people who could smooth out the tension with Bernie, and one them is Joe Biden Joe BidenSenate Republicans face tough decision on replacing Ginsburg What Senate Republicans have said about election-year Supreme Court vacancies Biden says Ginsburg successor should be picked by candidate who wins on Nov. 3 MORE,” said one Democratic strategist.

The potential problem, say observers, is that Biden and Clinton might find it difficult to get past the tensions that bubbled up last summer and fall as Clinton’s campaign wavered and supporters of Biden openly pressed him to take her on in a primary.

“Obviously, if Hillary is the nominee, he and President Obama will be behind her 1,000 percent,” said one Democratic donor who supported the Draft Biden effort. “But that doesn’t take away the fact there are some continuing frustrations.”

Democrats loyal to Biden and some of his advisers felt Team Clinton boxed them out of the Democratic race. They argue it is natural for the sitting vice president of a two-term president to consider running for the White House as an heir-apparent candidate.

“Going back a few months, it bordered on this intense rivalry, and there was a resentment about all the establishment support that fell behind Hillary,” a Democratic donor said.

Clintonites, for their part, were irked at Biden for trying to take credit for his support of the raid on Osama bin Laden’s compound in Pakistan when it was Clinton who counseled Obama in meetings to conduct the raid. As Clinton suffered through a difficult few months on the campaign trail, it was irritating to see Biden — who was also mourning the loss of his son Beau from cancer — hem and haw over a White House decision.

While both Clinton and Biden allies say tensions have cooled and reports of friction between the two are overblown, some of the strain lingers, according to those on both sides.

“Some of the statements he has made in recent months haven’t been exactly helpful,” said one Clinton ally.

Clinton supporters point to public comments made by Biden that appeared to telegraph a preference for Sanders’s idealism over Clinton’s pragmatism.

“I like the idea of saying, ‘We can do much more,’ ” Biden told The New York Times.

“I don’t think any Democrat’s ever won saying, ‘We can’t think that big — we ought to really downsize here because it’s not realistic,’ ” he added. “C’mon, man, this is the Democratic Party! I’m not part of the party that says, ‘Well, we can’t do it.’ ”

Sanders later seized on Biden’s comments to rally his supporters.

“I think the vice president is exactly right,” the Vermont senator said last week at a Pennsylvania rally. “That is what this campaign is about.”

At the same time, Biden has also offered public statements that seem to favor Clinton.

He recently said he’d like to see a woman elected president, a comment widely viewed as a near-endorsement of Clinton’s campaign.

“This country is ready for a woman,” Biden told the news website Mic when asked if Clinton faces added scrutiny because she is a woman. “There’s no problem. We’re going to be able to elect a woman in this country. I would like to see a woman elected.”

There have been reports of Clinton’s campaign bristling at public remarks by Biden, who is famous for going off script.

In January, after Biden said Clinton was “relatively new” to the income inequality issue, a Biden aide fielded a call from Jennifer Palmieri, Clinton’s top communications adviser, who said his comments were “wrong,” according to a report in The Wall Street Journal. A day later, Biden walked back the comments in a television interview.

Biden aides say the vice president thinks highly of Clinton, and the two have spoken several times during the course of the campaign.

And at a campaign event in Biden’s home state of Delaware, which hosts its primary on April 26, Clinton called the vice president’s passion for the country “truly inspiring.”

Biden, who, like Obama, is officially neutral in the race, was in nearby Philadelphia on Tuesday campaigning for Senate candidate Katie McGinty.

“The vice president has a strong relationship with both Secretary Clinton and Senator Sanders,” Biden communications director Kate Bedingfield wrote in an email. “As he has said many times, he plans to play an active role in campaigning for and supporting the Democratic nominee.”

Biden’s supporters believe he could help Clinton unify the party in the general election by exciting pivotal Democratic constituencies, such as organized labor.

Clinton is weak with white men, and Democrats think Biden could be particularly useful with that group in a general election against Republican presidential front-runner Donald Trump Donald John TrumpObama calls on Senate not to fill Ginsburg's vacancy until after election Planned Parenthood: 'The fate of our rights' depends on Ginsburg replacement Progressive group to spend M in ad campaign on Supreme Court vacancy MORE.

“I think that having the VP’s support would be incredibly important to Hillary, assuming she is the nominee,” said Jon Cooper, former national finance chair for the Draft Biden super-PAC.

“It would be one of the best ways to unify the party, because Joe Biden is so well respected, not only by his supporters, but also by the various factions within the Democratic Party.”

Cooper said he has spoken to numerous Sanders supporters who call the vice president their “clear second choice.”

“Next to having Elizabeth Warren Elizabeth WarrenBiden's fiscal program: What is the likely market impact? Warren, Schumer introduce plan for next president to cancel ,000 in student debt The Hill's 12:30 Report - Presented by Facebook - Don't expect a government check anytime soon MORE strongly endorse Hillary or be her running mate, or an endorsement from Sanders, I think the next best thing to that would be Joe Biden,” Cooper said.

Biden voted early in the Delaware Democratic presidential primary. He declined to say which candidate he supported on the ballot.

“I voted,” he said when asked by a reporter Monday about which candidate he voted for. “I voted.”