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Not long ago, commentators were declaring that “Bernie Sanders’ revolution is coming” and “It’s Bernie’s party’s now.” Pundits were delivering eulogies over the supposedly lifeless body of Joe Biden’s campaign. The moderate candidates in the Democratic presidential race who hadn’t yet dropped out were lagging behind Sanders. The only chance of stopping the Vermont senator’s socialist takeover of the Democratic Party, aides to Michael Bloomberg insisted, was for Biden to exit the race.

Now, over the course of four days, Biden has won at least nine states and, when all the results from Super Tuesday are tabulated, may end up with a delegate lead. As of late last night, FiveThirtyEight projected that he’s almost twice as likely as Sanders to finish the race with the most pledged delegates. It’s as dramatic a turnaround as has ever occurred in a presidential primary campaign. What happened?

One big answer is that today’s Democratic Party isn’t like the GOP in 2016. Four years ago, many ordinary Republicans wanted to overthrow their party establishment. After the 2020 primary field thinned, leaving Biden as the leading centrist candidate, ordinary Democrats showed at the polls yesterday that they like their party’s establishment just fine.   

To grasp the difference between the two parties, compare Biden with the 2016 Republican contender whom, on paper, he most resembles: Jeb Bush. Like Biden, Bush was closely associated with his party’s last president. Like Biden, Bush led in early polls. Like Biden, Bush struggled in debates. Like Biden, Bush performed horribly in Iowa, where he came in sixth, and New Hampshire, where he came in fourth. And, like Biden, Bush staked his candidacy on a comeback in South Carolina.

Bush’s strategy in the Palmetto State was similar to the one Biden employed last month: He made himself the defender of his party’s old guard. At a debate in South Carolina one week before voters there went to the polls, Bush drew a contrast between the insurgent Donald Trump’s nativism and former President George W. Bush’s more welcoming message. The “great majority” of immigrants, Jeb declared, “are coming to provide for their families. And we should show a little more respect for the fact that they’re struggling.”

Jeb also went out of his way to defend his brother’s response to 9/11. At the debate, when Trump accused George W. Bush and his advisers of having “lied” when “they said there were weapons of destruction” in Iraq, Jeb struck back. “While Donald Trump was building a reality-TV show,” he replied, “my brother was building a security apparatus to keep us safe. And I’m proud of what he did.”

The younger Bush, The New York Times noted, “seems to be embracing his inner dynast, joking about his family in speeches, pointing out relatives in his crowds and going out of his way to speak with pride about his father’s and brother’s achievements.” Two days after the debate, he brought his brother to South Carolina to campaign. Standing with Lindsey Graham—the state’s Republican senior senator—George W. told a North Charleston crowd that, “If serving as president of the United States makes me part of the so-called establishment, I proudly wear that label.”

Biden did something similar this year. Although he failed to secure Barack Obama’s endorsement, Biden made his relationship with the former president the centerpiece of his South Carolina campaign. His surrogates reprised Obama’s campaign chant, “Fired up, ready to go.” The former vice president referred endlessly to the “Obama-Biden” administration in speeches and used Obama as a battering ram against his opponents. One Biden ad accused Bernie Sanders of trying to “destroy Obama’s legacy” by replacing the Affordable Care Act with Medicare for All. Another slammed Sanders for having considered “challenging our first African American president in a primary” in 2012. And just as Jeb Bush leaned on an endorsement from Graham, Biden touted his support from Jim Clyburn, the long-serving Democratic representative from South Carolina.

The results could not have been more different. Bush lost to Trump in South Carolina by 25 points, and quickly dropped out of the race. Biden beat Sanders by 29 points and, buoyed by a new series of high-profile endorsements, went on to beat him in a slew of other states last night.

Why did embracing his party’s establishment work for Biden but not for Bush? Because Democrats like their establishment more. Although progressive activists criticize Obama, his approval rating among Democrats as a whole—according to Real Clear Politics’ polling average—is almost 87 percent. That makes Biden’s association with him an almost unmitigated political strength. By contrast, an internal Bush campaign poll showed that Jeb’s family connections turned many voters off. The “Bush stuff was holding him back,” one aide told The Washington Post.

Obama isn’t just personally more popular among Democrats than George W. Bush was among Republicans. His agenda is more popular too. Eighty-five percent of Democrats approve of Obamacare. By contrast, a May 2015 poll found that only 54 percent of Republicans believed that the Bush administration’s signature initiative—the Iraq War—had been worth fighting.

Sanders wants to radically expand upon Obama’s legacy. But he hasn’t frontally challenged it, because it’s broadly popular among Democrats. Trump, by contrast, made his assault on the GOP establishment’s support for immigration the centerpiece of his campaign. Soon after entering the race, he released a video slamming Jeb for calling immigration an “act of love.” At the debate a week before the South Carolina vote, he derided Bush as “so weak on illegal immigration it’s laughable.” It worked. According to exit polls, Trump beat Bush by 48 points among South Carolina Republicans who said immigration was their top issue.

By the time he left the race, Jeb Bush had a net favorability rating among Republicans of only five points. Biden’s net favorability among Democrats last month, by contrast, was almost 50 points. That discrepancy isn’t simply a function of the two candidates’ performances on the stump. It’s a statement about the party establishments they represent. Asked to explain Bush’s failure, Mike Murphy, the chief strategist for the former governor’s super PAC, explained, “Our theory was to dominate the establishment lane” but “the problem was there was a huge anti-establishment wave. The establishment lane was smaller than we thought it would be.”

In the Democratic Party, by contrast, the establishment lane is turning out to be larger than many people just last month thought it would be. Sixty-one percent of Democratic South Carolina primary voters said Clyburn’s endorsement of Biden played an important role in their choice. That kind of influence isn’t possible in a party in which voters loathe their leaders. It certainly wasn’t possible in the GOP in 2016, when Graham—far from being able to bolster Jeb Bush through his own endorsement—had a net negative approval rating among Republicans by the end of the primary campaign.

Biden could still lose. But his sudden comeback should put to rest facile comparisons between the Sanders and Trump insurgencies. Sanders and Trump aren’t just radically different politicians. They are operating in radically different partisan environments. Four years ago, many Republicans wanted to blow up their party. Last night, Democrats demonstrated that they do not.

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