Maria Herrera, 62, says Hispanic heritage would not be a sole reason for her to vote for a presidential candidate. (Ronda Churchill/For The Washington Post)

Maria Herrera, a 62-year-old retired casino housekeeper, feels no affinity for Marco Rubio even as he aims to make history as the first Hispanic president of the United States. As she explained: “He’s Cuban. I’m Mexican.”

“Rubio says things that are not good for Mexicans,” Herrera said, adding that she supports Hillary Clinton. “I would never vote for him just because he’s Latino.”

Rubio, whose parents are from Cuba, and Ted Cruz, whose father was born in Cuba, are competing to be the first Hispanic in the White House — and casting unprecedented attention on the nation’s growing Hispanic vote.

But in several key swing states — Nevada, Colorado, Florida and Virginia — most Latinos are not Cuban. Most lean Democratic — and identify more with their country of origin than with the broader terms, Hispanic or Latino, for those from Spanish-speaking countries. Most also oppose both Rubio’s and Cruz’s positions on immigration reform. All of that, in addition to long-standing tensions between Cuban and Mexican immigrants, could dash the GOP’s hopes that Cruz or Rubio could do what few Republicans have been able to do in a presidential election: attract significant Hispanic support.

Mexicans account for nearly two-thirds of the Latinos in the United States — about 35 million people. Cubans are the third-largest group, after Puerto Ricans, with just 2 million people, or only 3.7 percent of the Latino vote, according to the Pew Research Center.

In interviews in wedding chapels and casinos, all around this city of stretch limos, slot machines and neon signs, Mexicans who make up so much of the workforce said it would be far more meaningful to elect the first Mexican American president than the first Latino. Many said they would vote for a non-Latino over a Cuban American.

In two days of interviews, not a single Mexican said he or she supported Rubio or Cruz, and even some Cubans said they don’t plan to support either Cuban American candidate.

Part of the friction between Mexicans and Cubans comes from the starkly different reception they get when they arrive in the United States. Cubans who reach U.S. shores are almost automatically granted residency and eligibility for food stamps and other welfare benefits because of a special policy for those coming from the communist island — many arriving through Mexico. Mexicans who enter without legal papers live under the threat of deportation.

There are cultural distinctions, too. They speak with different accents, celebrate different customs and eat different foods. Mexico is soccer-obsessed, while Cuba loves baseball.

“Except for the fact that they both speak Spanish, everything else is totally different,” said Carlos Artiles, 50, a bartender at the Florida Café Cuban Bar & Grill, where the eggs come with stuffed potatoes and fried plaintains. Artiles, a Cuban, quickly became a citizen, but he sees firsthand how Mexicans, including his wife, try unsuccessfully for years and “pay thousands of dollars to attorneys to help. It’s completely unfair.”

“No way” will Mexicans rally around presidential candidates just because they are Cuban, he said.

“Like oil and water” is how Alejandro Carrillo, a Mexican salesman, describes Mexicans and Cubans. He said he believes that Cubans have it easier in the United States and often act as though they are better than Mexicans. As he shopped in Moda Latina, looking at cowboy boots and hats, Carrillo said the differences between Cubans and Mexicans extend right down to how they dress: “I never once saw a Cuban who wore boots.”

About 30 percent of Nevada’s population and 20 percent of its electorate is Latino. Mexicans far outnumber any Latino group here, but Cubans command an outsize influence.

Cuba had a thriving casino business when Fidel Castro seized control in 1959, and many Cuban casino workers fled the island and moved to this gambling mecca. For decades, Cubans have been influential in business, Spanish-language media and politics — just as they are in South Florida, home to the greatest concentration of Cubans.

Otto Merida, a prominent Cuban here who ran the Latin Chamber of Commerce for 40 years, said, “It would be a dream to have a Cuban American in the White House,” and he likes Rubio.

But early on, Merida signed up to support former Florida Gov. Jeb Bush. “If he could catch fire,” Bush would do very well with Mexican Americans because he is married to a woman born in Mexico, he said.

Andres Ramirez, a Democratic strategist in Nevada, said that despite differences, many Cubans and Mexicans get along. Some Hispanics — no matter the nationality — will vote for a candidate “just because they’re a Latino, just like some people will vote for a woman because she is woman — but that is not the majority.”

“Surnames can matter, but people vote on policy and platforms,” Ramirez said.

Rubio, whose wife is the daughter of immigrants from Colombia, has shown more ability to win over non-Cuban Hispanics in Florida than Cruz has in Texas, when they ran their Senate races, according to exit polls. Rubio campaigns, in both English and fluent Spanish, about being the son of immigrants who came to America for a better life for their children.

But Fernand Amandi, managing partner of Bendixen & Amandi International, which frequently surveys the Hispanic community, said that in a presidential election, Rubio will face much more intense opposition because Democrats will highlight the fact that he yanked his support for comprehensive immigration reform. Cruz unequivocally — “today, tomorrow, forever” — opposes giving citizenship to millions of undocumented immigrants, a great number of whom are Mexican.

Not all Mexicans interviewed were in the country legally, and some have legal status but not citizenship, and so they are not eligible to vote. But those Mexicans who are citizens, such as Herrera, who was washing her clothes in a laundromat, said they plan to vote for Clinton. The Republicans and Democrats are holding caucuses in Nevada next month, in the first primary-season voting in the West, right after Iowa and New Hampshire.

Herrera said she was more interested in having the first female president than the first Latino president. What Clinton says is more appealing to her than what she hears from Rubio or Cruz, she said.

Many Cubans lavished praise on Rubio, who lived in Las Vegas as a child while his father worked as a hotel bartender and his mother as a maid. A few said they like Cruz but not enough to consider voting for him.

And several Cubans said they support Trump, the candidate most despised by Mexicans. Trump has referred to some Mexicans as “rapists” and promised to build a gigantic wall on the border to keep Mexicans out.

“Trump says what others won’t. He fears nothing,” said Elizabeth Abad, 46, who left Cuba a decade ago, became a U.S. citizen and works at the Florida Café. “I like his toughness.”

Sergio Perez, 47, owner of the Florida Café and the Havana Grill, where Rubio recently held a big rally, also thinks Trump is the best candidate “in these difficult times.” Perez said people are anxious and cannot afford the same life — not even the same amount of groceries — they once had. “Nobody felt good this Christmas,” he said, adding that Trump, a businessman, knows how to build things and put people to work.

“It’s a dream to have a Cuban guy as president,” he said about Rubio, whom he called “a beautiful guy, smart, charming. He could be a great vice president.”

But don’t expect Mexicans to vote for him because, Perez said, “Eighty percent of the Mexicans don’t like the Cuban people.”