SACRAMENTO, Calif. (Reuters) - Democrats seeking to unseat Republican U.S. President Donald Trump in 2020 will choose from the largest and most diverse set of candidates in history - yet, so far, two older white men are leading the pack.

FILE PHOTO: Twenty four 2020 Democratic presidential candidates are seen in a combination from file photos (L-R top row): U.S. Senators Bernie Sanders, Kamala Harris, Elizabeth Warren, Cory Booker, Amy Klobuchar, Kirsten Gillibrand, Michael Bennet and former U.S. Senator Mike Gravel. (L-R middle row): Former Texas congressman Beto O'Rourke, U.S. Representatives Tulsi Gabbard, John Delaney, Eric Swalwell, Tim Ryan, Seth Moulton, former HUD Secretary Julian Castro and former U.S. Vice President Joe Biden. (L-R bottom row): Mayor Pete Buttigieg, Former Gov. John Hickenlooper, Gov. Jay Inslee, Andrew Yang, Marianne Williamson, Mayor Wayne Messam, Montana Gov. Steve Bullock and New York City Mayor Bill de Blasio. REUTERS/Files/File Photo

The early dominance of former Vice President Joe Biden, 76, and U.S. Senator Bernie Sanders, 77, is raising uncomfortable questions about whether Democratic voters think a woman or minority candidate has what it takes to defeat Trump, the likely Republican nominee.

Women candidates played a key role in Democrats regaining control of the U.S. House of Representatives last year. But they still face greater hurdles than men in seeking executive offices, and there is division in the party about what kind of candidate is best suited to win in November 2020.

“How do you beat Big Daddy Trump? One of the ideas is that you beat him with Big Daddy Joe,” Christine Pelosi, daughter of House Speaker Nancy Pelosi and chairwoman of the California Democratic Party’s women’s caucus, said in reference to Biden.

Pelosi, who has not endorsed a candidate, did not say if she agrees with that assessment. She thinks a woman ultimately will end up on the Democratic ticket.

Ten of the 24 Democrats seeking the nomination are minorities or women.

They are all polling behind Biden and Sanders, who are getting the most support among Democrats in all demographic groups, including minorities, Reuters/Ipsos opinion surveys show.

Democratic strategist Rose Kapolczynski, who ran campaigns for former U.S. Senator Barbara Boxer, said that is not just because they are white men. “It’s because they’re well known and liked among Democratic voters,” she said.

She also said public debates this summer will give other candidates a chance to better introduce themselves to a national audience.

Biden has raced out to a strong early lead, helped by his name recognition and a sense among many voters that he may have the best chance of beating Trump in battleground states.

Stefanie Brown James, a strategist and cofounder of the Collective PAC, which backs and trains progressive African American candidates, said Biden is respected by African-Americans for his role in the administration of Barack Obama, the nation’s first black president.

“For the black community especially, this is a man who was an elder statesman who made the decision to be the number two to the first black man running for the office,” she said. “Speaking of privilege and ego, not a lot of people would do that.”

In Memphis, a predominantly Democratic and majority black city, Senator Elizabeth Warren, who is white, and Senator Kamala Harris, who is of African-American and Indian descent, have devoted followings among Democrats of color, said Corey Strong, a former local party chairman. Senator Cory Booker, an African-American man, is also popular, he said.

But most people he has talked to still cite Sanders or Biden as their eventual pick, he said, in part out of concern that the other contenders will not be able to defeat Trump.

“A lot of people (are) saying, ‘I like this person’ but also saying ‘I want a guy that can win as well,’” Strong said.

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Women and minority candidates fighting for attention in a crowded field also must overcome ingrained prejudices that affect voter choices.

Women are less likely than men to be chosen for executive offices such as president, according to research by the Barbara Lee Family Foundation, which studies elections.

While people will vote for a man they do not like, they generally will not vote for women they dislike, the research shows. And women must show they are strong enough to keep the country safe.

“If she’s going to be the decision-maker, voters have to be that much more convinced that she’s qualified,” said foundation spokeswoman Amanda Hunter. “There are even more barriers when they run for executive office if they happen to be women of color.”

The result is an unfair playing field, tilted against women and minority candidates as they vie for media coverage, donations and votes, said Toni Van Pelt, president of the National Organization for Women.

“We are concerned about the never-ending narrative about ‘electability’ that seems to indicate that a candidate must be white and male to win,” Van Pelt said. “This notion has been knocked down repeatedly with the election of Barack Obama and, despite Russian interference and pervasive sexism, Hillary Clinton winning the popular vote in 2016.”

Harris has taken on the electability question on the campaign trail. At a speech in Detroit, she said the debate is often too simplistic by suggesting “certain voters will only vote for certain candidates” and overlooks the voices of black and female voters in places such as the Midwest.

Many party activists and voters say the Democratic nominee should be anyone who has the charisma, fortitude and support to defeat Trump - regardless of gender or race.

Voter Aleia White, 32, agrees. She would prefer, however, that the eventual nominees for president and vice president reflect America’s diversity.

“It’s important that the ticket represent our country,” White said at a recent campaign event for Warren in Ohio. “We’re not all white men.”