The supposed bipartisan group No Labels recently complicated Trump's calculus by ending its bid to find a candidate to run. That leaves anti-vaccine activist RFK Jr., Green Party candidate Jill Stein, and Harvard professor Cornel West as potential spoilers to Biden's reelection, either individually or as a group. Kennedy, who polls highest and has the resources to potentially get on the ballot in all 50 states, poses the biggest threat.

It remains to be seen whether Kennedy's candidacy—which draws interest from conspiracy theorists and Kennedy-nostalgic Democrats alike—will hurt Biden or Trump more in November. But some polling suggests that Kennedy is currently skimming more voters away from Biden.

What is clear is that Trump benefits disproportionately from every third-party candidate in the race since he fell several points shy of reaching 50% in both 2016 and 2020. By contrast, Biden won in 2020 with 51% of vote—just barely enough to tilt the Electoral College in his favor. It’s telling that Kennedy's presidential bid has been bankrolled by one of Trump's biggest donors, Mellon banking heir Timothy Mellon, and championed by one of Trump's biggest allies, Steve Bannon. Not so coincidentally, a key Kennedy campaign official, Rita Palma, also said her No. 1 goal was blocking Biden's reelection bid. Palma has since been axed by the Kennedy campaign.

All that said, it is incumbent upon the Biden campaign to blunt Kennedy's allure among Democrats to make him a bigger drag on Trump in November.

“If Kennedy makes it on the ballot in these states—and that’s a big if—we’re going to make sure voters know how extreme his policies are and that MAGA megadonors are bankrolling his spoiler campaign to be a stalking horse for Donald Trump,” said Democratic strategist Lis Smith, who is advising the Democratic National Committee on the matter.

The Kennedy family itself, with its enduring star power among Democrats, has been searching for ways to kneecap RFK Jr., who's leveraging the family name while damaging the Kennedy legacy with his antithetical stances.

But at some point soon, the Biden campaign will have to deploy a strategy to neutralize Kennedy's Democratic appeal, and a recent Engagious focus group in Pennsylvania of 11 Trump-to-Biden swing voters may offer a window into one potential avenue.

According to Axios, roughly half of the swing voters who participated in the focus group said the candidates' stances on abortion would play a role in how they voted in the fall.

Six of those swing voters also said they would vote for Kennedy over Biden and Trump, but questions about Kennedy's abortion stance became an immediate hang-up for them.

"If he doesn't agree with what I agree with abortion, then I'm going to switch," said participant Michael W.

Rich Thau, the focus group moderator and president of Engagious, said that pro-choice swing voters who expressed support for Kennedy "seemed to second-guess their support when confronted with the argument that a vote for Kennedy is effectively a vote for Trump and his abortion policies."

After some initial jostling last year, Kennedy told NBC News’ Ali Vitali that he supported abortion during the first three months of pregnancy but would sign a federal abortion ban if elected.

“I believe a decision to abort a child should be up to the women during the first three months of life," Kennedy said. "Once a child is viable, outside the womb, I think then the state has an interest in protecting the child." The exchange between Kennedy and Vitali was captured on video, making it fodder for attack ads.

Kennedy’s campaign has since backtracked on those remarks, issuing a statement saying he does not support a federal ban on abortion.

“Mr. Kennedy supports a woman's right to choose,” says the statement, adding that it’s “not up to the government to intervene in these difficult medical and moral choices.”

A national abortion ban is a nonstarter with Democratic voters, and perhaps most importantly, many Democrats who aren't thrilled about voting for Biden but would never consider voting for Trump.

In a follow-up exchange with Daily Kos, Thau said, "For pro-choice Trump and Biden voters, the risk posed by voting for RFK Jr. could be too much if abortion is a top-tier concern."

He added that he hasn't yet come across another issue that "would have the same effect on RFK-curious swing voters as abortion does. It’s not to say there aren’t such issues … but I haven’t pushed or probed on those yet."

Whatever the range of issues that could dissuade Democrats from voting for Kennedy, abortion appears to offer the Biden campaign a starting point.