“Sanders would be every holiday present rolled into one,” Sean Spicer, the former White House press secretary and an ex–senior adviser to a pro-Trump super PAC, told me. “With Bernie, there’s a general agreement that he’s a gift.”

Mistreating Sanders and alienating his supporters could cost Trump the election, depending on how the Democratic nomination fight ends. An analysis from the political scientist Brian Schaffner shows that in 2016, tens of thousands of Sanders supporters voted for Trump in Wisconsin, Michigan, and Pennsylvania—three battleground states that Trump narrowly flipped from blue to red. Had these voters aligned with the Democrats instead, Hillary Clinton would have won all three states and, ultimately, the election.

“To the extent that a Democratic primary becomes close and maybe Sanders doesn’t get the nomination, there’s a good chance that a reasonable share of his supporters is likely to buy into the thinking that the party had it in for Sanders,” Schaffner, a Tufts University civics professor, told me. “And if that’s the case, some of those people might find it easy to sit out a general election or cast a protest vote.”

Read: What Bernie Sanders’s 2020 rivals learned from Hillary Clinton

Sanders could also prove a tougher opponent than Trump reckons: He has grassroots backing, plenty of money, and a version of the same populist message that propelled Trump’s 2016 upset victory. Democratic operatives see a deep cynicism, not solicitude, in Trump’s approach. “Trump feels that he can attract the support Bernie has—that’s all,” Tad Devine, a top adviser to Sanders’s 2016 campaign, told me. “I don’t think he likes Bernie.”

Every corpuscle of Trumpworld appears dedicated to propping up Sanders. One obvious tip-off that Trump is trying to promote Sanders’s candidacy: He’s relatively sparing in his insults. Master of the raw and indiscriminate putdown, Trump will demean just about anyone: teenage climate activists, Gold Star families, and deceased lawmakers alike. But when it comes to Sanders—who, let us not forget, has called Trump a “pathological liar” and a danger to the republic—the president often sounds like a fanboy, if not a Bernie Bro. Even his nickname for Sanders, “Crazy Bernie,” is mild by Trumpian standards.

The counterpuncher isn’t counterpunching much at all—not yet, anyway. “People like his message. He’s got energy,” Trump said about Sanders to reporters in the Oval Office earlier this month.

Since the summer, Trump’s campaign has spent only about $25,000 on Facebook ads that mention Sanders, often lumping him in with other Democrats, according to an analysis by Bully Pulpit Interactive, a Democratic communications firm that also examined the Trump campaign’s Facebook ads targeting Biden. (The Trump campaign declined to comment on its advertising strategy.)