COLUMBIA, S.C. — Sen. Elizabeth Warren (D-Mass.) took hip-hop artist and activist Benny Starr to Bertha's Kitchen, a black-owned restaurant in North Charleston, where she ate collard greens and cornbread but passed on the fried chicken and sweet tea.

Former New York mayor Mike Bloomberg has pummeled the airwaves in South Carolina, Nevada and Super Tuesday states with ads, so much so that a questioner at a Tennessee news conference thanked him for a $3.5 million buy at his media station before proceeding.

Former vice president Joe Biden rushed to South Carolina the night of last week’s New Hampshire primary, abandoning a state that would disappoint him with a fifth-place finish in favor of one flush with the nonwhite voters on whom he has staked his candidacy. He has since spent four days in Nevada.

“You can’t be the Democratic nominee,” Biden said in Columbia that night, “unless you have overwhelming support from black and brown voters.”

After two contests in states with overwhelmingly white electorates, the Democratic presidential primaries are rushing into a broader and more diverse landscape where Latino and African American voters play a potentially decisive role — and are up for grabs.

Just as more voters of color are poised to assert their say in the primary, the battle for their support is growing more competitive. Biden, who has been both popular among Latinos and the longtime polling leader among black voters, enters this phase as a weakened candidate.

His chief rivals — who like him are white — all boast spotty records on race or have demonstrated other weaknesses that pose steep challenges as they seek to appeal to a powerful and skeptical electorate.

Nonwhite voters have been left to evaluate past actions and future promises as the candidates try to ingratiate themselves by tweaking applause lines, translating campaign themes into Spanish, and filling the airwaves with images of themselves working alongside the first black president.

“You’re now seeing voters of color, who are the backbone of the Democratic Party, particularly black women, flex their electoral muscle,” said Bakari Sellers, a former South Carolina state legislator and influential Democrat in the state. “My mom and her friends will decide who the nominee is and who goes toe to toe against Donald Trump.”

A third of voters in Nevada, whose caucuses conclude Saturday, are Latino or black. In South Carolina, which votes on Feb. 29, nearly two-thirds of expected Democratic voters are black. Most Democratic voters in the 2016 Texas and Alabama presidential primaries were nonwhite, according to exit polls, as were more than a third of the voters in Arkansas, Tennessee, Virginia and North Carolina. All of those states, along with heavily minority California, will vote on Super Tuesday, March 3.

“This is the season where the candidates will now face the Democratic Party. By that I mean the diversity that is the strength of the party,” said Donna Brazile, a longtime strategist who served as interim Democratic Party chair during the 2016 election.

Biden’s unsteady turn — a fourth-place finish in Iowa preceded his decline in New Hampshire — has given an opening to rivals to make their own arguments to black and Latino voters. Bloomberg and another billionaire candidate, Tom Steyer, already have made inroads among black voters, polls have suggested.

Sen. Bernie Sanders (I-Vt.) successfully attracted young Latino and African American voters in Iowa and New Hampshire, and has risen in polls among nonwhite voters in other states as well. But he has had difficulty attracting older nonwhite voters, who are more reliable at casting ballots.

In Nevada, he has begun advertising in Spanish-language ads; in South Carolina he has leaned on endorsements from young, black members of the legislature. His national surrogates, including former Ohio state senator Nina Turner and Black Lives Matter activist Shaun King, routinely tout Sanders’s record of involvement in the civil rights struggle going back to the 1960s. In a controversial opinion piece that bashed Biden in Columbia’s State newspaper, Turner said Sanders has led “a movement that has been fighting for racial and economic justice since the civil rights era.”

Warren has, like Sanders, been working to build support among nonwhite voters for months, albeit with fewer financial resources. On Monday, her campaign launched a new outreach effort entitled Latinas en la Lucha — “Latinas in the Fight.” She has also worked to create kinship with black women, although the efforts have so far fallen largely flat, according to polls.

“The electability factor that the Bidens have used in their campaign has been seriously moved to the column of uncertainty because of Iowa and New Hampshire,” said Rev. Al Sharpton, a civil rights leader and MSNBC host. “It leaves the black vote wide open. At the same time, it’s a question of who can penetrate that. It’s a different terrain.”

Biden also has been hit by rivals for his past support of crime bills whose stiffer sentences impacted nonwhite communities and for having touted how he worked as a senator with colleagues who were segregationists. In response, he has leaned on his long relationships with African Americans and Latinos, and his service as Barack Obama’s vice president.

“Too often, your loyalty, your support, your commitment to this party have been taken for granted,” Biden said last week in Columbia. “I have never once in my career, since I got involved as a kid, taken you for granted. And I give you my word as a Biden, I never, ever, ever will.”

He spoke of his time as a public defender and a county councilman, when he fought against redlining.

“And by the way,” he added, “I had the back of a great president, Barack Obama, for eight years.”

Rosemary Lawrence, a 75-year-old black woman who leads the political ministry at Charlotte’s mostly black Friendship Missionary Baptist Church, represents Biden’s biggest worry. She supported Biden when he entered the race in April, laying out the argument for anyone who asked that he was the candidate most likely to defeat Trump. But not anymore.

“I love Joe Biden,” she said. “I really love him. Because he was so supportive and so helpful to [Obama]. They did great things together. Especially health care. And you know, I really wanted to support him, but what I’ve seen recently is he doesn’t seem to be as energized and focused and alert as he was, say, eight years ago even.

“And now his funding is drying up. The bottom line is I want to find somebody who can beat Donald Trump.”

Early voting has already started in North Carolina. Next week, Lawrence plans to cast a ballot for Bloomberg.

Bloomberg, however, has his own problems. As New York mayor, he pushed a stop-and-frisk program that aggressively targeted nonwhite men for police searches, which he defended until issuing an apology days before entering the presidential race. He has also come under fire for other comments critical of young black men and others.

His Democratic rivals have accelerated their criticism of him as he prepares to be on ballots for the first time in the Super Tuesday contests.

“When you peel back the layers of Bloomberg, it’s devastating,” Sellers said, offering a list that included Bloomberg’s past support for New York’s policing approaches and his support for then-Michigan Gov. Rick Snyder’s handling of the water crisis in the mostly African American city of Flint. “You look at the utterly disgusting way he spoke about black men after stop-and-frisk, his policies. He’s not a racist but he implemented racist policies.”

Bloomberg’s strategy so far has been to overwhelm other candidates with paid advertising, including in South Carolina via stations at historically black colleges and universities. While his crowds, even in southern states, are often affluent and white, he is regularly introduced by black leaders who testify to Bloomberg’s understanding of the history of racism in the country and his commitment to nonwhite voters.

Bloomberg has been endorsed by more than 100 mayors, many of them black. He has proposed a plan, named “the Greenwood Initiative” for a black Tulsa community destroyed in a 1921 racial massacre, that sets a goal of helping 1 million black families buy a home, double the number of black-owned businesses and triple the net worth of a typical black family.

“I am committed to using the power of the presidency to right the wrongs of institutional racism,” Bloomberg told a mostly black crowd last week in Houston, decorated with a sign announcing a new branding effort, “Mike for Black America.”

Steyer has dotted the Palmetto State’s freeways with billboards and spent generously on television ads. Jonathan Metcalf, the South Carolina state director for Steyer’s campaign, said Steyer has ascended in state polls not just due to those tactics but because he has invested in campaign infrastructure and in the communities he hopes will turn out to vote for him.

“Ninety-three percent of our organizers are African Americans. Most are females. Sixty percent of those are organizing within 20 miles of where they grew up,” Metcalf said. He said Steyer also has made a point of investing in African American residents, including the contractors and caterers at campaign events.

In some ways, Steyer’s success in South Carolina is proof that another candidate can eat into the lead that Biden has held among black voters since he entered the race. But it would not be easy, or quick: Metcalf said Steyer’s campaign has been building its infrastructure in South Carolina since last summer.

That reality complicates the task for candidates who have surged recently, including former South Bend, Ind., mayor Pete Buttigieg and Sen. Amy Klobuchar (D-Minn.). Each has benefited overall from stronger-than-expected showings in the first states but face both a lack of familiarity and pointed accusations as the contest broadens to highlight nonwhite voters.

As mayor, Buttigieg fired South Bend’s first black police chief and has been accused of having only a superficial understanding of the needs of black America — and the black residents of the city he headed. He also faced outrage from some black South Bend residents after a white police officer shot and killed a black man — a controversial moment the officer failed to capture with his body camera. At a town hall following the shooting, one audience member yelled, “We don’t trust you.”

He has argued that nonwhite voters simply don’t know enough about him yet. In Nevada, he has built an organizing team that his campaign says mirrors the demographics of the state. Over 40 percent of his team there speaks Spanish, and a third identify as Latinx.

In one new ad airing in Nevada, Buttigieg looks directly into the camera and begins to speak in Spanish. Quiero que imagines el primer dia despues de la presidencia de Donald Trump, ” he says. “I want you to picture the first day after the Donald Trump presidency.”

In South Carolina, he, like Bloomberg, has touted plans meant specifically to appeal to African American residents with investments and policy changes.

“I’ll be very attentive to the ways in which just the culture and the climate and the tone can help build up a sense of belonging, backed up by all the policies we’re going to do,” he said during a recent campaign event at Claflin University, a historically black college in Orangeburg, S.C.

Klobuchar is only now able financially to try to organize in states beyond Iowa and New Hampshire, putting her at a stiff deficit. Like Buttigieg, she has been hit for past actions, including decisions while a Hennepin County prosecutor not to bring charges against police who killed residents, and for aggressive prosecutions that critics said disproportionately affected nonwhite communities.

She has campaigned on her efforts to go after white-collar criminals and expand voting rights. Along with Buttigieg, she launched a Spanish-language ad; unlike him, she is not the narrator.

“Amy will bring back to the White House the respect it deserves, will fight to give us better health care, better prices on our prescription medicines and the best education for our loved ones,” the ad says. “Amy knows what’s important: our well-being.”

Bernice Scott, a former Richland council member who leads the South Carolina grass-roots organizing group known as the “Reckoning Crew,” warned that ads and endorsements will not be enough. Her group has thrown its support behind Biden.

“We’re not as stupid as people think we are. Throw some money down and say, ‘I’m better for you than anyone else.’ We know history. It’s a history here,” Scott said. “We aren’t just going to change our minds.”

That remains Biden’s biggest hope, even if his popularity among nonwhite Democrats appears to have weakened. His campaign has sent 100 paid canvassers to South Carolina and Nevada, where the campaign is “all in,” said senior campaign adviser Symone Sanders. Biden also has ads running in the top four television markets in the state, reaching 85 percent of South Carolinians.

“Joe Biden is not new to these communities,” she said, citing the decades he has spent as a candidate and as vice president. “They know him.”

In Nevada, Biden’s campaign had hoped for the endorsement of the mostly Latino Culinary Workers Union, but the group announced last week it would not side with a candidate. In South Carolina, Biden could benefit from the endorsement of his longtime friend, House Majority Whip James E. Clyburn, the longest-serving member of Congress from South Carolina and the state’s most powerful Democrat.

Clyburn — who has faced countering pressure from his grandson, who works for the Buttigieg campaign — said last week that he hasn’t decided whether he will endorse, or who his nod would go to.

“I think I might be inclined to make an endorsement,” Clyburn said in an interview. “I haven’t ruled it out.” If he did endorse, he said it would only come in the final days of the race in South Carolina, after the Feb. 25 debate in Charleston.

Josh Dawsey in South Carolina contributed to this report.