WASHINGTON — The last Democrat to win the presidency was a black man who combined the voting power of people of color with white liberals to win in a way no one had before.

Now, Sen. Kamala Harris' rise in the polls after last week's debate has some wondering if she's the candidate who can reunite the vaunted Barack Obama coalition.

The question turns the notion of electability — an obsession for many Democratic primary voters — on its head, and would have been inconceivable just a week ago, before Harris hit former Vice President Joe Biden on the debate stage in Miami with a personal and powerful attack on his opposition to forced busing to integrate schools.

Several post-debate polls show Harris has pulled herself close enough to the front-runner to yank him down a rung or two, while chipping away at Biden's two key strengths — his support from African American voters and the perception that he has the best chance of beating President Donald Trump.

"The polls demonstrate that there's a new standard of electability — building trust with black voters and speaking authentically and powerfully about racial justice," said Aimee Allison, the founder of a network for women of color called She the People.

"Black voters want a leader that can stand up to accommodation in a party that often takes them for granted," Allison continued.

Harris' support among African Americans has climbed sharply in most post-debate surveys, though Biden still leads.

In a Quinnipiac poll Tuesday, Biden's support among black Democrats dipped to 31 percent from 48 percent in their June poll. Harris, on the other hand, saw her support among black Democratic voters grow to 27 percent, compared with 11 percent in June. Overall, the survey found the contest in a virtual tie — 22 percent for Biden to 20 percent for Harris.

In 2008, Obama didn't consolidate support among African Americans in early voting South Carolina until after he proved he could win white voters in Iowa.

Strong turnout from minority voters, along with young, educated and liberal whites helped him beat Hillary Clinton in the primary and then win the general election by expanding the electorate rather than fighting for a sliver of swing voters.

Like Obama, Harris hails from her party's establishment, but is a relatively fresh face with only two years under her belt in the Senate. And she has some progressive positions that could also make her appealing to younger, more liberal voters.

Rep. Bobby Rush, D-Ill., a prominent member of the Congressional Black Caucus, was one of several lawmakers and local officials who threw their support behind Harris after the debate, arguing she could make an appeal across racial lines.

"There is no question that Kamala is the only candidate prepared to fight for all Americans against a Trump administration that has left them behind," Rush said. "More importantly, she has a vision for the nation that looks to the future and centers her policy around a lived experience that cuts across geography, race and partisanship."

Of course, no votes in the primary will be cast for another eight months and plenty will change before then, let alone before the general election next November.

And recreating what Obama did is easier said than done. Democrats Andrew Gillum in Florida and Stacey Abrams in Georgia both tried some version of the approach in their high-profile gubernatorial campaigns last year and each fell short.

Many of the most successful Democratic candidates in the 2018 midterms were powered by a very different coalition, led in part by white suburban women fed up with Trump.

But Democrats may be beginning to see that their party has multiple potential paths to beating Trump and that trying to win back white working-class voters in the Midwest is not the only one.

A new HuffPost/YouGov poll found the perception of Harris' and Massachusetts Sen. Elizabeth Warren's electability each climbed 10 percentage points after the debate. Biden, meanwhile, went from 70 percent of respondents saying he was capable of beating Trump in May to 57 percent after the debate, though that is still higher than any other candidate.

In just five minutes on stage in Miami, Harris managed to do what no other candidate has done in five months: Disrupt Biden's double-digit polling lead, the most consistent and persistent dynamic of the 2020 Democratic primary.

The former vice president wasn't pushed from his perch leading the field, above 30 percent in the polls, when women came forward to say his touching made them uncomfortable. It didn't move when he changed his position on federal funding of abortion, nor did it appear to waver when he touted his ability to work with segregationist senators.

And it stayed steady as former Texas Rep. Beto O'Rourke, South Bend, Indiana, Mayor Pete Buttigieg and Warren all saw rises and falls behind him.

"Sen. Harris has always shown the potential to be a breakthrough candidate," former Obama spokesman Ben LaBolt said. "Her Biden critique catapulted her not only because she delivered it effectively but because it was a generational critique, delivered with personal authenticity, that also showed how effective she would be attacking Trump."

Harris has tried to capitalize on the debate by rolling out new endorsements, and her campaign announced this week that she's hiring 30 more staffers in Iowa and another 25 in New Hampshire.

But the same volatile forces that helped Harris vault the field in less than a week will also force her to find a way to keep up the momentum off the debate stage.

"Now it's a matter of sustaining what have been some very compelling moments into a more continual cadence," LaBolt said.