Joe Biden, fighting for his political life, has made a surprise move to the left wing of the party. Biden has always carefully calibrated his politics to be close to the median position of his party, which is why Axios described him as “long a centrist Democrat.” But now, under siege, Biden has become a born-again progressive—perhaps even a leftist.

Over the last two weeks, he’s announced support for a wide swath of policies tailored to please left-wing Democrats: new rules banning medical debt from being used in credit ratings and a push for total medical debt relief, term limits and an enforceable ethics code for the Supreme Court, and new legislation limiting rent increases from corporate landlords to 5 percent per year, among other newly elevated proposals.

Axios describes this batch of policies as part of Biden’s “rescue operation” involving a “left leap to survive.”

The leading instigators of this “left leap” are Senator Bernie Sanders, the Squad (led by Representative Alexandria Ocasio-Cortez), the Congressional Progressive Caucus, and the Congressional Black Caucus. These individuals and groups have become the unexpected fortress of Bidenism, shielding the president from attack even as centrists like Representative Angie Craig (D-MN) and Representative Adam Smith (D-WA) turn on him.

As Axios reports:

Progressives also have cheered Biden’s recent moves.

After the Congressional Progressive Caucus had a call with Biden, Representative Brad Sherman (D-Calif.) told Axios the president teased many policies the caucus wants—which he said is “not a complete coincidence,” based on where Biden is now drawing support on Capitol Hill.

“This is his base,” Sherman said of the Progressive Caucus, “You see who has called upon him to move on, and who has called upon him to stay, and the Progressive Caucus lines up with those who have asked him to stay.”

Sanders penned an effusive op-ed in the New York Times for Biden’s reelection over the weekend, and Rep. Alexandria Ocasio-Cortez (D-N.Y.) also has been publicly supportive.

This embrace by progressives and leftists is matched by the fact that the anti-Biden faction in the party is now headed by centrists such as Representative Adam Schiff (who is running to fill Diane Feinstein’s Senate seat in California). Schiff is a longtime close associate of former House speaker Nancy Pelosi, hence a good barometer of where the party elite stands.

It might seem topsy-turvy for centrists to go knives-out on Biden even as the left embraces him; it’s certainly not a turn of events that could be predicted by Biden’s lifelong commitment to middle-of-the-road liberalism.

But the current alliances make sense when you realize that the elected Democrats who are most at risk by Biden’s staying on as candidate are centrist Democrats in swing districts and purple or red states. These Democrats are facing a real existential threat, as Biden’s unpopularity could unleash a red wave that swallows up their political support. Conversely, progressive and left-wing Democrats tend to represent very safe blue seats. They’ll survive even a Biden wipeout.

From the point of view of Bernie Sanders and the Squad, they have much to lose if they oppose Biden. In the past, as in Representative Jamaal Bowman’s losing primary fight earlier this year, centrists made much hay out of bad-faith arguments that Bowman betrayed Biden’s agenda by occasionally voting against it (in fact, Bowman voted in opposition to centrists watering down Biden’s proposals). It’s in the Squad’s interest to avoid such accusations in the future.

Further, if the congressional left did come out strong against Biden, that could make centrist politicians and donors more pro-Biden in reaction. Cynically, one could say that the proper left view of the Biden mess is that the centrists created the monster of the aging Biden presidency, so it is their job to clean it up.