Joe Biden is a man on a mission: to defeat Donald Trump in November and recapture “the soul of this nation.”

The former vice president is well on his way to taking the first step towards that goal after having turned his dire presidential prospects around with a series of primary victories that have no parallel in U.S. political history. Biden has won the Democratic presidential primary, knows he is the victor, and is beginning to act like it.

All of which points to an inevitable question for Bernie Sanders: when should the 78-year old political revolutionary suspend his campaign and start helping Joe Biden on the stump? 

If politics were simply about numbers, Bernie Sanders would have likely made the decision to leave the race last week when he suffered a gut-wrenching 15-point defeat in Michigan. Including Super Tuesday, Sanders has lost 17 of the last 23 contests, including in states where he was projected to win (Texas, Massachusetts, Maine, Michigan, and Washington State). For Sanders, the primary schedule over the next two months is about as treacherous and chilling as Mt. Everest is for the average hiker. Biden is leading in Arizona by 20 points. Sanders will get blown out of the water in Florida. And he is a virtual afterthought in places like Maryland, Georgia, and Connecticut later this spring. Biden’s 153-delegate lead may not sound impressive, but it’s getting more insurmountable for Sanders by the week. Moderate Democrats are wondering aloud: “why on earth would Bernie Sanders stay in a race he is destined to lose? What purpose does it serve?” As David Frum wrote in the Atlantic a week ago, "The only thing they [the Sanders movement] can actually do by prolonging Sanders’s campaign is sustain Trump in his work of defamation against Biden.” 

It’s not an altogether unreasonable point to make. There are many people in the Democratic Party, including Hillary Clinton, who firmly believe that you can trace a dark, black line connecting Donald Trump’s squeaker of a victory in 2016 to Sanders staying in the Democratic primary until the very end. Bernie’s supporters find that reasoning faulty, if not laughable. You can’t, for instance, blame low African American turnout in the city of Detroit on Bernie Sanders. Nor can you blame Bernie for the fact that Clinton didn't campaign in Wisconsin during the general election under the assumption that the Badger State’s electoral votes were guaranteed to drift into the Democratic column. But the complaint still percolates deep in the bowels of the Democratic Party establishment—and members of that establishment are deathly afraid that a similar situation could occur this year.

Bernie may be a career politician (he was first elected to public office in 1981 and has been a lawmaker in Washington since 1991), but he is anything but a conventional one. He is part-politician, part-activist. If staying in the race is necessary to bolster the progressive platform or spread the ideals that power his movement, it’s highly likely he will continue to give speeches on the stump and spar with Biden on the debate stage regardless of how out-of-reach the nomination is. The septuagenarian believes he is winning the ideological contest within the Democratic Party, even if this isn’t being reflected at the ballot box. The pragmatic voice on his right shoulder would counsel him to gracefully bow out, endorse Biden, and work hard over the remainder of the year to bring millions of his supporters into the vice president’s camp. However, the activist voice whispering in Bernie’s left ear—the one we all saw at last weekend’s audience-free debate in Washington, D.C.—is telling him to spread the gospel far and wide until the very last primary.

As a former Sanders adviser told Politico on March 17: "I think he’s in. Who is going to advise him to drop out?”   

There is nobody better than Jane Sanders, Bernie’s wife and closest adviser, to help us decipher why the Vermont senator continues to press forward. “It’s never been about only winning the election,” she told New York Times Magazine writer Robert Draper for his Sunday feature on Bernie Sanders. “I mean, if you won just because you were the one with the superior campaign strategies, that would not be terribly satisfying in the end. It’s much more satisfying to pick up the paper, go online or watch TV and see town halls of people questioning their senators about Medicare for All from a more informed point of view...That’s been so moving to see, really. So gratifying.”  

In other words, for Bernie, the 2020 presidential election isn’t just about how many delegates can be accrued, how many states can be won, and how much money can be raised. His campaign is much more important than those typical metrics. It’s about ensuring that the values, principles, and policies Bernie Sanders has represented for 40 years—making health care a universal, cost-free right; forcing the uber-wealthy to pay more taxes; transforming the American political system into one that works for the vast majority of people rather than special interests; and taking a hammer to the political status-quo—are not only protected but enhanced. 

This is the kind of bull-headiness Biden’s advisers find nauseating, particularly in a year that will determine whether Donald Trump will receive another four years in the Oval Office. But for Bernie Sanders, the grumblings from the Democratic establishment are part of the territory. They may very well propel him to keep going.

Daniel R. DePetris is a columnist at the Washington Examiner and a contributor to the National Interest. 

Image: Democratic U.S. presidential candidate Senator Bernie Sanders speaks during the 11th Democratic candidates debate of the 2020 U.S. presidential campaign, held in CNN's Washington studios without an audience because of the global coronavirus pandemic, in Washington, U.S., March 15, 2020.