GOP U.S. presidential candidate Donald Trump speaks with his son Eric (right) at his side after the Florida, Ohio, North Carolina, Illinois and Missouri primary elections during a news conference held at his Mar-A-Lago Club in Palm Beach, Florida March 15, 2016. REUTERS/Joe Skipper

As he stood surrounded by family on a stage in Palm Beach, Florida, after winning three state primaries Tuesday, Republican front-runner Donald Trump once again boasted that he had united the party.

"We have something happening that makes the Republican party probably the biggest political story in the world," the billionaire said, noting he had seen huge lines Tuesday outside polling centers. "Millions of people are coming into vote ... Democrats are coming in, independents are coming in, and — very, very important — people who have never voted before. It's an incredible thing."

Trump has bragged for weeks that he is expanding the Republican party, adding "millions and millions" of voters and insisting that Latino and African-American people "love" him. But the vast majority of his supporters are white men — at a time when the number and influence of diverse voters is growing. Even if Trump's presumptive rival, Hillary Clinton, doesn’t appeal to minorities or young voters as much as Barack Obama did in 2008 and 2012, Trump probably can't win with white voters alone this November.

Here’s what we know: The number of people casting ballots for Trump is higher than the number of people who cast ballots for 2012 GOP nominee Mitt Romney, according to International Business Times calculations. Through Super Tuesday, Trump had about 3.37 million total votes. Romney, at this point, had 3.28 million — even though seven more states had voted.

We also know that more Republicans have turned out to vote in state primaries than usual. Pew Research Center reported that through the first 12 primaries, GOP turnout had included 17.3 percent of eligible voters. In 2012, it was 9.8 percent. Meanwhile, Democratic turnout this year was 11.7 percent, up from 2012 but down from 2008.

What we don't know is how Trump's coalition of white men will play eight months from now. "There's only so many of them," said Adrian Gray, a strategist who used to work for the Republican National Committee.

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For decades, white men dominated the electorate and pushed Republican candidates to the presidency — think Gerald Ford, Ronald Reagan and George H.W. Bush. But that strategy didn't work for 2012 GOP nominee Mitt Romney, who lost to Obama despite winning 62 percent of white male votes nationally. Politico calculated that Trump would need 70 percent of white men on his side to win the White House.

The nonwhite share of the American population is expanding, and fast. By 2043, the U.S. is expected to have a majority minority, which means lawmakers will have to appeal to nonwhite groups whether they want to or not. The GOP appeared to come to terms with this fact in a 2013 autopsy report released after Romney’s loss, which largely blamed the lack of inclusive messaging for the party's defeat.

“The Republican Party is one of tolerance and respect, and we need to ensure that the tone of our message is always reflective of these core principles. In the modern media environment, a poorly phrased argument or out-of-context statement can spiral out of control and reflect poorly on the Party as a whole,” it wrote. “Thus we must emphasize … the importance of a welcoming, inclusive message in particular when discussing issues that relate directly to a minority group.”

That's the opposite of what Trump has done. From his June campaign announcement, where he called Mexican immigrants criminals, drug dealers and rapists, to this weekend's clashes with black protesters after his refusal to condemn the Ku Klux Klan, his actions have proven controversial and often divisive. Party leaders, including Romney and House Speaker Paul Ryan, have denounced Trump’s candidacy, as have party elders like Sen. Ben Sasse, R-Neb., Karl Rove and Glenn Beck.

“A Trump nomination could alter the electoral math, the geography, in some very interesting ways that are outside the bounds of what we’ve seen in recent elections,” said Michael McDonald, an associate professor from the University of Florida in Gainesville who runs the United States Election Project website. “We don’t really know how this is supposed to work.”

If Trump could make in-roads with white as well as black, Latino and Asian voters, in each case getting the GOP 3 percent more support than it received in 2012, eight states could flip from blue to red, according to FiveThirtyEight. But that's probably not happening. News reports about Latinos in Nevada and Florida supporting Trump should be "taken with the hugest grain of salt that you could possibly take," said McDonald, noting that in most cases, the number of nonwhite voters turning out to vote in GOP primaries has been too small to analyze properly.

Obama performed well among minorities in 2012, nabbing 93 percent of African-Americans', 71 percent of Hispanics' and 73 percent of Asians' votes. The 2016 Democratic presidential nominee — presumably Clinton, who was leading her rival Bernie Sanders in delegates Tuesday night — may not be as successful with these groups but is still predicted to win a majority of minorities.

In Florida on Tuesday, for example, Clinton had the support of 79 percent of black Democrats and 72 percent of Latinos, who made up 28 and 20 percent of the electorate, respectively. In Illinois, Clinton won 70 percent of black Democrats and 50 percent of Latino ones, who made up 27 percent and 8 percent of the electorate respectively, according to CNN exit poll data.

That means Trump will need to rely on white voters.

Trump, who has cast himself as a Washington outsider who understands conservatives' frustration with bureaucracy, has proven popular among white, non-college-educated, working males so far, said Stuart Rothenberg, the founding editor and publisher of the Rothenberg and Gonzales Political Report based in Washington, D.C. In a December Rasmussen Reports poll, 41 percent of white voters said they'd support Trump if he were to match up in a general election against Clinton.

Individual states also suggest Trump is inspiring Republicans to head to the polls. In Illinois, for example, about 350,000 new voters have registered since 2012, according to ABC News. In Florida, about 140,000 more Republicans registered to vote this year than did in 2012.

"There's no doubt that more people are turning out to vote in the Republican contests. The question is are they overwhelmingly Democrats who have switched parties, people who have never voted, or is it primarily Republicans who don't normally vote in primaries? We don't know yet," Rothenberg said. "He may just be activating a wing of the Republican party."

Whether the white male vote is enough to nab Trump a victory in November is dubious, partly because primary data doesn't always link up with general election results, said Gray, the strategist.

For example, in Michigan in 2012, about 996,000 people voted in the GOP primaries — an increase of about 15 percent from 2008, according to IBT calculations. But in November, Romney only received about 3 percent more votes than Republican nominee John McCain did in 2008, and Romney lost the state. By that measure, the fact that Republican primary voters increased by nearly 33 percent in the state might not mean much.

Another reason is that for every voter Trump attracts with his polarizing rhetoric, he alienates another — not just minorities but also people who lean socially liberal or find themselves offended by his comments. A January Gallup poll that found the billionaire had a -25 net favorable rating, with 58 percent of people labeling him as unfavorable. Some Americans may cast ballots for Clinton only to oppose Trump.

“I find it just so implausible that we could have this massive white nativist mobilization without also provoking a big mobilization among minority voters,” political scientist Ruy Teixeira recently told the New Yorker. “It is kind of magical thinking that you could do one thing and not have the other.”

In the end, a candidate needs 270 electoral votes to win the White House in November. In 2012, Obama nabbed 332 — and a totla of 65.9 million votes from a variety of groups.

Trump himself seemed to acknowledge the stakes Tuesday night on stage in south Florida. "We have to bring our party together," he urged.