Now that Sen. Elizabeth Warren has officially left the race, her supporters are faced with a decision: Do they cast their lot in with the progressive standard-bearer, Sen. Bernie Sanders, or opt for former Vice President Joe Biden?

On the surface, it seems as if Warren supporters might be more inclined to vote for Sanders. After all, the vast majority of Warren’s voters in the Super Tuesday states for which we have exit polls identified as somewhat or very liberal (81 percent), which might make them seem like they’d be more ideologically simpatico with Sanders. But there are several reasons that her supporters might not move en masse to Sanders’s camp.

For one thing, Warren has yet to endorse either Sanders or Biden. And several recent polls have found that her supporters’ second-choice picks are fairly equally divided between Biden and Sanders. Morning Consult, for instance, found that 43 percent of Warren supporters would opt for Sanders as their second choice, while 36 percent would choose Biden. And a recent Ipsos/Reuters poll found that Warren supporters’ second-choice loyalties were evenly split, with 47 percent picking Sanders, and 46 percent backing Biden.

But perhaps most troubling for Sanders: He was particularly weak with one of Warren’s key demographic groups — white college-educated women — on Super Tuesday, suggesting that it might not be easy for him to draw these voters into his fold. White college-educated women weren’t Biden’s strongest group, to be sure, but he still outpaced Sanders by 15 percent points with this core piece of Warren’s base. (Granted, Biden did well with white voters generally.)

College-educated white women were Warren’s base Share who supported each candidate on Super Tuesday by race, gender and education, from exit polls Answer BIDEN SANDERS WARREN Other White college-educated women 36% 21% 28% 14% White women, no degree 43 28 12 17 White college-educated men 38 29 16 16 White men, no degree 37 37 10 12 Super Tuesday states for which exit poll data is available are Alabama, California, Maine, Massachusetts, Minnesota, North Carolina, Oklahoma, Tennessee, Texas, Vermont and Virginia. “Other” includes all of the remaining candidates who respondents said they were voting for on Super Tuesday, including candidates who dropped out. Nonwhite support was not broken out by gender and education.

There’s also evidence that Warren voters’ views on the issues don’t line up neatly with either Sanders’s or Biden’s base of supporters. According to an analysis of aggregated surveys in the field from Jan. 9 to Feb. 13 administered by Democracy Fund + UCLA Nationscape, USA Today found that all three candidates’ supporters have about the same levels of net support for many key issues in the Democratic primary, like limiting how many bullets a gun magazine can hold or offering a public option for insurance. But on a few key policies, Warren supporters actually backed issues at rates more similar to Biden supporters than Sanders supporters.

For instance, net support for policies like debt-free college was at similar levels among Warren voters and Biden voters, although Biden has offered a considerably more moderate plan than either Warren or Sanders. Biden’s proposal would prioritize making a two-year community college education — not a four-year college degree — free for students. Similarly, Warren supporters fall between Biden and Sanders supporters in their net support for Medicare for All, even though it was a policy that she and Sanders both championed. But there are other issues, like the Green New Deal, that Warren supporters are much more likely to back than Biden voters are, making them more similar to Sanders supporters on those points. The variation suggests that even on policy issues, Warren’s supporters might not be as much of a shoo-in for Sanders as many might assume.

The exit polls also indicate that many Warren supporters aren’t making their decision on the basis of ideology alone. On the one hand, a clear majority (59 percent) of Warren voters say they want a president who will be more liberal than Barack Obama, while only 32 percent say they want a return to Obama-era status quo. That might seem like bad news for Biden, whose entire campaign pitch is a return to the Obama administration. But most Warren voters also prioritize electing someone who can beat Trump — and Biden did much better than Sanders among voters who shared that sentiment. Only 30 percent of Warren supporters said they prefer a candidate who agrees with them on the issues over one who has a good chance of winning in the general election, while 67 percent say their main priority is to choose a candidate who can beat Trump.

So Warren’s departure might not be as much of a boon to Sanders as some of his allies hope. Winning over white college-educated women could be particularly challenging for Sanders, since he performed the worst of these three candidates among this group on Super Tuesday. His support in this group was especially low in states like Virginia, which has a large population of highly educated voters in its northern suburbs. In total, 51 percent of white college-educated women voted for Biden in Virginia, while 18 percent voted for Warren and only 15 percent went for Sanders.

This suggests that Sanders will continue to struggle among white college-educated women even now that Warren has left the race. And without an endorsement from Warren, he could see a significant number of his progressive frenemy’s supporters fall in line behind Biden.

Laura Bronner contributed research.