Bernie Sanders has money, a passionate base of support, and a will to battle for his cause for however long it takes, Elizabeth Warren is his ideological soulmate, and you would think that at some point, should he fail to secure the Democratic nomination, she would be the natural heir to his support. But you would be wrong.

“All the evidence that I have reviewed suggests Elizabeth Warren is not the automatic beneficiary of Sanders dropping out,” says Bill Galston, a senior fellow at the Brookings Institution. “There is more of a crossover between Sanders and Biden than one might imagine.”

That’s good news for former Vice President Biden, who holds a steady but tenuous lead in the crowded field, but who would fall to a distant second if the support for Warren and Sanders were combined. But the race is more complex than that, says Galston, a veteran of six presidential campaigns, and a senior fellow at the Brookings Institution.

Sanders and Warren are on friendly terms and even have a so-called non-aggression pact, forged before both announced their candidacies, not to directly attack each other. Yet a Pew poll in August, when Warren was on a roll in the media, showed her picking up only three of every 10 Sanders votes (29 percent) should he leave the race.

For more recent data, at The Daily Beast’s request, Quinnipiac University Poll director Douglas Schwartz had his team look at their last few national polls, and they found that Warren is the second choice for about a third of Sanders voters while Biden is the next most popular second choice with one fifth of Sanders voters. “No other candidate consistently hits double digits,” Schwartz said in an email.

Galston says more data is needed but speculates that a “gender dynamic among white working-class men” could be part of Warren’s under-performing with Sanders voters. “It is striking that compared to Warren, both Bernie and Biden do relatively well among working-class voters,” he says.

With no votes cast yet, these dynamics are still fluid, “but there’s no doubt the Sanders constituency is quite different than Warren’s,” says Dave Wasserman with the non-partisan Cook Political Report. “His support skews younger. It’s a little less white and a little less college-educated than Warren.”

Many observers think Sanders will remain in the race even if he doesn’t finish in the top tier in Iowa, where he is faltering. Should he then fall short in New Hampshire, a state he dominated in 2016, he could be left with a largely symbolic campaign, but people familiar with his thinking say he would remain in the race “to hold people’s feet to the fire.”

We could get an early taste of that as Warren struggles to answer the question of how she will pay for Medicare for all, and whose taxes will rise to foot the bill for a program with no realistic chance of passing Congress even with a Democrat in the White House. Without 60 Democratic votes in the Senate, a near impossible goal for the foreseeable future, Warren might as well be tabulating the number of angels on the head of a pin.

Still, if she tries to amend her support for Medicare for all, the bill that Sanders wrote and that she backs, he will call her out on it as a betrayal of trust, not necessarily of himself as a mentor and friend, but of the American people.

“Her choice is a blast from Bernie now or rejection from the voters in the fall,” says Galston. “Life would be easier for Warren if he’s out of the race, freeing her up to make certain gestures to the center of the party with moderate cost to the left. But I can’t see him dropping out, and he won’t be forced out by lack of money.”

Sanders got a much needed jolt for his campaign when Rep. Alexandria Ocasio-Cortez (AOC) and activist filmmaker Michael Moore endorsed him at a huge “Bernie’s Back” rally in Queens, New York. It was the largest crowd for any Democrat so far in this campaign season as Sanders sought to allay qualms about his health and stamina following his recent heart attack.

Campaign manager Faiz Shakir said in an email that “Bernie’s staying power comes down to trust. He is the candidate working Americans can trust to take power from those who have it and give it to those who need it because that’s what he’s done his whole life. It is that trust in Bernie that will bring more and more Americans into the process, and they will help the senator sweep Donald Trump out of the White House and create a political revolution to transform our country.”

If there is a protracted close delegate race between Biden and Warren, Sanders could have leverage. Under Democratic primary rules, any candidate who reaches 15 percent gets a share of delegates.

Under these rules, Beto O’Rourke could potentially win a bundle of delegates in Texas, and Kamala Harris in California, assuming they’re both still in the race on March 3, Super Tuesday, when 10 states are voting. Sanders is not the only potential kingmaker, but he is the only one unlikely to be forced out of the race for lack of money, or sidelined by a political reality he doesn’t accept.