The Obama coalition of young people, women and people of color turned out in large numbers for Biden, especially in large metropolitan areas. Biden improved modestly on Hillary Clinton’s margins from four years ago across most segments of the electorate, though he appears to have done less well with Latinos. But Biden also relied on support from disaffected Republicans and independents, while containing Trump’s massive advantage with working-class whites — a tenuous alliance Democrats will not be able to bank on in future elections.

In its breadth, the Biden coalition represents a toehold for Democrats to appeal to a variety of voting blocs across the spectrum. But its limitations were laid bare in the party’s down-ballot disappointments. It failed to deliver a Senate majority, left the Democratic House majority with a weakened hand and face-planted in legislative contests in states like Pennsylvania, New Hampshire and North Carolina.

It’s an ominous sign for the party as it prepares for runoff Senate elections in Georgia in January and midterm elections in two years.

The Biden coalition “is very broad, and it’s very shallow,” said Paul Maslin, a Democratic pollster who worked on the presidential campaigns of Jimmy Carter and Howard Dean. “The ‘Demographics is Destiny’ kind of new Democratic coalition is … not getting there anywhere near as quick as people would hope.”

As the Biden era opens, Democrats have largely held or expanded their core voting blocs, while gaining with independents and in suburbia. But it is a patchwork federation, not a wholesale realignment — the election failed to show convincing signs that the electorate is moving more permanently to the left.

In what amounted to a referendum on Trump, Biden’s supporters were primarily motivated by a desire to defeat the Republican president. There is no guarantee that the disparate groups will remain together in the absence of a galvanizing opponent like Trump on the ballot.

“The big challenge for Democrats for the next cycle is how are you going to get all of these Democrats back to vote in a midterm,” said Chuck Rocha, who was a senior adviser to Bernie Sanders and architect of his Latino outreach effort. “I think we have to get better at talking to people … at starting earlier to talk to Black and brown voters.”

In many ways, Biden was a model candidate to compete with Trump. He appears to have done better than Clinton with both young voters and seniors, according to exit polls. He drove people of color to the polls in metropolitan areas, and he prevented Trump from running up the score with his white base.

Moreover, according to exit polls, Biden defeated Trump in the suburbs, where most of America’s votes are cast. That is a significant gain — and the foundation of Biden’s coalition – reflecting the party’s emerging strength in increasingly diverse suburbs four years after Trump narrowly beat Clinton there.

The shift came despite appeals to suburban voters from Trump that were more overt than any president since Richard Nixon. Biden won overwhelming margins in Democratic-leaning suburbs, like those around Philadelphia and Detroit, and more modest victories in conservative oriented suburbs, where he drew Trump’s 2016 margins down. Even in Republican-heavy Texas, Trump carried suburban counties by about 8 percentage points less than he did in 2016, according to the Texas Politics Project at the University of Texas at Austin.

If Democrats can continue to make headway in the suburbs, the election last week suggested the type of urban-suburban alliances that could power the party’s resurgence in the Sun Belt, a critical component of the Republican coalition.

It’s already happening in Georgia, where Biden combined exploding turnout from people of color with a dramatic improvement over Clinton’s performance in the diverse suburbs of Atlanta. In Gwinnett and Henry counties, which Clinton won by mid-single digits, Biden was beating Trump by closer to 20 percentage points. Biden is now leading narrowly in Georgia, which last supported a Democrat for president in 1992.

Of the city-suburban coalition around Atlanta, Celinda Lake, a Democratic pollster advising the Biden campaign, said, “It’s the new South … It’s the future of Democrats in the South.”

Antjuan Seawright, a South Carolina-based Democratic strategist, said that Biden relied on “some of the most consequential constituencies in all of our lifetimes … You can almost feel the gravity of the vote that was cast by Black people, because this was a life or death vote for Black people.”

Still, the story of 2020 was one of incremental — not tectonic — shifts. And Biden’s massive vote total belied the fact that Trump also received millions of votes more than in his 2016 bid.

“People expected these huge compressions [of Trump’s base voters] and huge margin increases from some of these constituencies, and it didn’t happen,” said Ruy Teixeira, a senior fellow at the Center for American Progress and an expert in election demographics.

The Biden coalition bears a resemblance to the Obama coalition, he said, but “there are clearly differences.”

For Democrats now, he said, “There’s no choice but to do better among white, non-college voters, and that’s partly what they were able to do in this election, right? What they really need to do is more … You can’t just rely on non-whites and educated liberals. That’s insane.”

The instability of the coalition was evident in the Latino vote — strong in some areas of the country, weaker in others. In Arizona, where Democrats aggressively courted Latino voters, Biden’s win was widely attributed to Latino enthusiasm in Maricopa County, where Biden won more than three-quarters of the vote in Latino-heavy precincts, according to the UCLA Latino Politics and Policy Initiative.

But Republicans made gains with Latinos in Florida and South Texas.

Fernand Amandi, a veteran Democratic pollster and consultant in Florida, said that “no matter how you decipher, unpack or investigate [Biden’s] victory,” the record-breaking popular vote total that he amassed amounts to a mandate. But he said that because of the uniqueness of Trump — and his “distorting” effect on the election, which confounded pollsters and moved voters in unpredictable ways — the composition of the Democratic coalition going forward may be less clear.

He said, “I don’t think we will know what the new Democratic coalition is until [Democrats] run against a Republican president not named Donald Trump.”

In the interim, Biden will have at least two years and a broad base of people who voted for him once to work from. His governing agenda has an opportunity to lock in support across segments of his coalition and unite in a more permanent way.

Because of the coalition’s breadth, Lake said, “It might be in some ways tougher, and you have to fight to get it out to vote … But it’s a better governing coalition” because of how broad it is. Biden’s political style may be especially well suited to coalition building — viewed broadly as more palatable than some other Democrats, such as Clinton.

The concern for Democrats is that voters whose primary motivation was ousting Trump do not necessarily represent a loyal constituency for the party in the midterm elections or in 2024.

Biden himself is acutely aware of the polarization of the electorate — and its fragmentation — calling in his victory speech on Saturday for cooperation between Republicans and Democrats in Washington. In part, his remarks were a reflection of the governing reality he will face, with a Senate that is likely to remain in Republican hands.

But it also spoke to the tenuousness of the coalition that put him in the White House.

“The last thing Democrats should be after this election is cocky about how it’s just going to get better and rosier and la-di-da in the future,” Maslin said. “This is still a tough, tough slog in this country.”

Looking forward to the midterms, he said, given last week’s down-ballot losses, “We’re not exactly dealing from a position of strength after what happened this year.”