DETROIT — From one of the key Midwestern states flipped by President Trump, Sen. Kamala D. Harris took aim at those who contend the most electable Democratic nominee will be one who connects with the white working-class voters credited with his victory.

“There has been a conversation about electability and who can speak to the Midwest,” Harris said Sunday night at an NAACP dinner here. Too often, she said, the definition of who matters in the Midwest leaves people out.

“It leaves out people in this room who helped build cities like Detroit. It leaves out working women who are on their feet all day — many of them working without equal pay . . . Our party is not white or black, Hispanic or Asian, immigrant or indigenous. It is all of us.”

The senator from California is not the only candidate trying to redefine “electability” for her own purposes, a task that has grown more acute since former vice president Joe Biden — who casts himself as best equipped to appeal to the white working-class voters prominent in the industrial Midwest — announced his candidacy last month.

If Harris was arguing for a broader racial definition of the party’s targeted voters, Sen. Elizabeth Warren (D-Mass.) recently cast the electability question in terms of gender.

“Are we going to fight because we’re afraid? Are we going to show up for people we didn’t actually believe in, but we were afraid to do anything else?” Warren said at last month’s She the People presidential forum. “That’s not who we are. That’s not how we’re going to do this.”

Sen. Bernie Sanders (I-Vt.) has made that argument from an ideological lens, arguing that his brand of democratic socialism makes him the most appealing candidate to voters still struggling economically.

“You’re going to hear a lot of folks, our political opponents, say, ‘Oh, Bernie can’t beat Trump.’ But, I would suggest, take a look at virtually every poll that’s ever been done,” he said at a town hall meeting in Fort Dodge, Iowa. He cited internal polling his campaign recently conducted showing him ahead of Trump in Michigan, Wisconsin and Pennsylvania, three states flipped by Trump in 2016.

The dispute over what kind of candidate is most electable reflects a divide that has convulsed the party since Trump defeated Hillary Clinton in 2016.

One camp believes the way to victory in the 2020 general election runs through the Rust Belt, with a nominee who can recapture the white blue-collar voters who backed Barack Obama in 2008 before siding with Trump.

Another camp argues that the Democrats’ best chance in 2020 will be to mobilize the blocs of voters that would more likely not vote than vote Republican. By building a diverse coalition that includes, among others, African American voters and the growing Latino population turning out in big numbers, Democrats could overcome what some of them believe is a fixed number of Trump voters. This theory holds that Democrats have more potential voters to add to their 2020 bloc than Trump does, as long as the right candidate emerges to generate excitement.

The debate remains ongoing because the 2016 election offered proof for both sides. According to a Washington Post analysis, Trump succeeded in expanding his reach among white working-class voters over the party’s previous nominee, Mitt Romney. At the same time, Clinton drew significantly fewer votes in predominantly black areas than Obama did in 2012.

That gives the current campaigns the ability to argue either side of the debate — as do new polls showing voters divided on which path they want the next nominee to take.

In the most recent Post-ABC News poll, Democratic and Democratic-leaning voters were fairly split when asked whether the Democratic nominee should be best positioned to win over more centrist independents like those in the upper Midwest versus energize the Democratic base. Forty-four percent said the Democratic Party nominee needs to attract independents, and 48 percent suggested the base. Among self-identified liberals, the split was 48 percent toward independent voters, and 45 percent to the party’s base. Among moderates and conservatives, the split was 44 percent to independents, 49 percent to the base.

No candidate is openly conceding any one group or another, nor openly targeting one group alone. Biden touts his Scranton, Pa., roots and old-school sensibilities in an attempt to appeal to white working-class voters. Yet he is counting on support among African American voters, too. Harris, seeking to become the first black woman elected president, is going out of her way to reach African American voters, but her teacher pay initiative and other outreach emphasize women more broadly.

Randi Weingarten, head of the American Federation of Teachers, introduced Harris at her town hall in Detroit, praising Harris’s teacher pay policy.

“And I don’t buy into that ‘women aren’t electable’ thing,” Weingarten said.

Harris’s campaign plans to utilize a hybrid strategy, one she took her first steps toward Sunday night: mobilizing minority voters in the Rust Belt. The strategy is based on voter turnout in the 2016 election, which found that had African American voters turned out for Clinton in the same numbers they did for Obama in 2012, she would have won Michigan, Wisconsin and Pennsylvania by small margins. That would have been enough for an electoral college victory.

Harris’s Sunday night speech recalled Obama’s approach in 2008, though Harris has been careful to distance herself from the former president to limit comparisons between the two. (Asked in Iowa if she considers herself “an Obama Democrat,” Harris said simply, “I call myself Kamala.”)

Obama, in a 2004 convention speech, spoke dismissively of the notion of a red America and a blue America, contending that there was only one United States. Harris noted on Sunday night that accenting the importance of working-class white voters “ignores our commonality and complexity.”

But Harris also has illustrated the difficulty of appealing to different blocs of voters. So far her schedule has taken her to historically black colleges and universities around the country, and has focused largely on younger and minority voters in the early states. Harris has traveled most often to South Carolina, where 60 percent of the Democratic electorate is African American.

That approach has its drawbacks when it comes to attracting support in largely white states. In New Hampshire, Harris has been criticized for not spending much time in the state. Harris added fuel to that notion when she told talk show host Trevor Noah that questions about her commitment to the state carried an “inference” that “the demographic of New Hampshire is not who you are, in terms of your race and who you are.”

Similar grumblings have percolated quietly in Iowa, which Harris has visited three times since announcing her campaign, including the day after her announcement. Although she has visited there as much as any state other than South Carolina, some Iowa Democrats suggest that Harris has not made her presence felt as much there as in other states.

The problem is that without strong finishes in the first two states, voters in later-voting states that are more diverse, such as South Carolina and Harris’s home state of California, may be tempted to move on to other options.

Other candidates are also trying to redefine what voters consider electability, especially when it comes to qualifications.

Biden’s argument has been that, given his decades in the Senate and eight years as vice president, he would come to the job equipped to tackle any crisis that emerges. And, he notes, he would have built-in support across the breadth of the Democratic Party.

Even before his entrance, candidates with less experience have sought to apply positive spin to political backgrounds that are far less expansive.

South Bend, Ind., Mayor Pete Buttigieg has challenged the idea that service in federal offices is a requirement. He contends that those who have to balance a budget and work across party lines to keep cities afloat might be more prepared to lead a divided country than those contributing to gridlock in Congress.

That is roughly the same argument put forth by Julián Castro, a former San Antonio mayor and Obama Cabinet member, who claims both executive and federal bureaucratic experience.

Beto O’Rourke has tried to cast himself as more than just a former congressman, and one who is uniquely qualified to solve one of the nation’s most in­trac­table problems: immigration and border security.

Their disparate arguments carry a unified undertone: Democrats spent much of 2016 mocking the notion that Donald Trump was electable — and then he won.

Annie Linskey and Sean Sullivan in Washington contributed to this report.