Welcome to Joe Biden’s dilemma.

His last remaining rival for the Democratic presidential nomination suspended his campaign. But, Sen. Bernie Sanders has pointedly refrained from endorsing the former vice president. And Sanders made it crystal clear that his name will remain on the Democratic primary ballot going forward, to gather delegates and ensure "influence" at the party convention.

SANDERS DUCKS QUESTION WHEN ASKED IF HE'LL ENDORSE BIDEN

For Biden – who needs the support of Sanders and his legions of young and progressive followers in order to unify the party as he challenges President Trump – a delicate dance is ahead. The former vice president clearly needs to embrace more of Sanders’ progressive agenda if he wants to seal the deal with that part of the base.

But going too far leaves Biden even more vulnerable to attacks from President Trump that he’s pushing a socialist agenda. Trump and his allies have hammered the message since the beginning of the cycle that the Democratic Party has drifted far to the left of most Americans. They are eager to paint Biden with that brush.

Within moments of Sanders' suspension, the president's re-election campaign went up with a digital ad highlighting similarities between the presumptive nominee and the democratic socialist.

“Bernie Sanders and Joe Biden: A big government socialist and a big government liberal,” the narrator in the spot says. “They’re more alike than you think.”

While withholding an endorsement, however, Sanders beckons Biden to embrace even more of his agenda.

“I hope to be able to work with Joe to move him in a more progressive direction,” Sanders said in an interview Wednesday night on the "Late Show" on CBS. “He's going to have to bring new people into his political world and he's going to have to listen to their needs, young people, working people, and maybe start moving in a different direction to some degree than he has in the past.”

Talks between the two teams to discuss areas of policy agreements are getting underway. “The two campaigns continue to be engaged on a range of topics that would build on Vice President Biden's existing policy proposals and further our shared goals to move the country forward,” a senior Biden campaign official told Fox News on Thursday.

BIDEN HOLDS EDGE OVER TRUMP IN NOVEMBER SHOWDOWN, ACCORDING TO NEW POLLS

Biden took steps in this direction even before Sanders bowed out. Last month he partially embraced the senator’s push for free tuition at public universities and colleges – which was a centerpiece of Sanders’ two White House bids. Biden also adopted a proposal for bankruptcy reform, which was a key component of Sen. Elizabeth Warren’s progressive presidential campaign.

And in his one-on-one presidential primary debate with Sanders last month, the former vice president pledged a moratorium on deportations under any circumstances during the first 100 days of a Biden administration.

On Thursday, Biden took two more steps, proposing to lower Medicare eligibility to age 60, and offering a plan to forgive all student debt for low- and middle-income borrowers who attend public colleges or historically black colleges and universities (HBCUs) and private, underfunded minority-serving institutions (MSIs)

But don’t expect Biden to embrace Sanders’ signature proposal – a government-run "Medicare-for-all" system.

“I mean, I don’t think Joe is likely to adopt my platform. I got that. All right,” Sanders acknowledged on Thursday night. “But if he can move in that direction, I think people say, ‘you know what, this is a guy who we should support and we'll support.’”

TRUMP CAMPAIGN TIES BIDEN TO SANDERS IN NEW AD

Biden’s hoping to avoid a repeat of the 2016 general election campaign, when Sanders – following a bitter nomination battle with eventual nominee Hillary Clinton – finally endorsed his rival in July. But many of Sanders’ supporters didn’t support Clinton, contributing to Trump’s upset victory in the November general election.

This time around, Sanders dropped out of the race well before the end of a primary calendar now extended due to coronavirus-related concerns with in-person voting. And the apparent bitterness between Sanders and Clinton isn’t so obvious this time around, as both the senator and Biden at least publicly highlight their friendship and mutual respect.

Add to that Sanders' repeated vow to do whatever it takes to defeat Trump in November.

THE LATEST FROM FOX NEWS ON THE 2020 PRESIDENTIAL CAMPAIGN

While winning Sanders over is step one, securing the support of his followers is a much larger step two.

The progressive group Democracy for America – which backed Sanders – pledged on Wednesday that “we are 100% committed to doing everything we can to ensure that Joe Biden beats Donald Trump.”

“And, after Joe Biden's wins, as we will make sure he does, the progressive movement will push him every single day to be the progressive president America demands and our challenging times require,” the organization added.

But the Progressive Change Campaign Committee – which was a top supporter of Warren’s White House bid – spotlighted that “nothing is more important for Biden right now than to actively show progressive voters that popular progressive ideas – which are needed in this moment – will be at the forefront of his agenda.”

The most high-profile Sanders supporters in Congress – progressive freshman Reps. Alexandria Ocasio-Cortez of New York, Ilhan Omar of Minnesota and Rashida Tlaib of Michigan – all took to Twitter to praise Sanders and lament the suspension of his campaign. But so far they've been silent on whether they'd back Biden.

So are Sanders' rank-and-file supporters ready to embrace Biden?

One of the senator’s top backers and surrogates in New Hampshire in 2016 and again in 2020 – executive councilor Andru Volinsky – told Fox News “there are people who have hurt feelings, concerns, they’ve worked very, very hard for a very long time and I think that needs to be respected.”

Volinsky – a Sanders delegate at the 2016 Democratic convention who’s running for New Hampshire governor this year – stressed that “I think the vice president would be making a strategic mistake were he to push too hard too quickly. I think people need some time and space to make decisions and I think they’ll make prudent ones once given a little bit of time.”

CLICK HERE TO GET THE FOX NEWS APP

And he advised that “the big policy issues that Sen. Sanders championed for so long need to be respected and adopted” by Biden.

Another leading Sanders supporter, who asked to remain anonymous to speak more freely, said that “personally I can [support Biden], but I know a lot of people who can’t. … A lot of people are really disappointed with the option that we’re left with right now.”

Fox News' Madeleine Rivera and Allie Raffa contributed to this report.