If Hillary Clinton is going to emerge from tomorrow’s Super Tuesday elections with her status as front-runner for the Democratic nomination intact, it will in large measure be thanks to people such as Antonio Álvarez.

“Barack Obama, he is a fine speaker, but we don't know him very well,” says this 69-year-old meat cutter outside his home in east Los Angeles. “We trust Hillary because of her husband — a good man — and we know she will help our community.”

Latinos are described by Mrs Clinton’s strategists as her firewall, or “contrafuegos”. These voters are expected to participate in greater numbers than before, accounting for a third of the Democrat turnout in California tomorrow and a significant portion of the electorate in half a dozen other states.

While Mr Obama has captured the overwhelming majority of black voters in recent contests — as well as a healthy share of whites — Latinos and Hispanics have skewed heavily towards Mrs Clinton by a margin of two, or even three, to one.

Bill Clinton, in a weekend appearance on the Eddie “Piolín” Sotelo radio show, went so far as to predict that Hispanic people “will determine the nomination of the Democratic Party and the next president of the United States”.

In his interview Mr Clinton stressed both his own record of support for Latinos when he was in the White House and his wife’s relationship with them, which dates back 35 years to when she worked with Raúl Yzaguirre, a Mexican-American activist, in Texas.

He also cited, approvingly, “our neighbours in the south” where Latin America’s matriarchal societies have already produced women presidents in Argentina and Chile.

There have, however, been hints of a more sinister secret to her support. Sergio Bendixen, a Clinton pollster, recently gave public voice to a view previously only whispered. “The Hispanic voter — and I want to say this very carefully — has not shown a lot of willingness or affinity to support black candidates,” he told The New Yorker magazine.

Although the Clinton campaign swiftly disavowed these remarks, there are tensions between two minority groups jostling against each other in America’s cities and competing for often low-paid employment.

A Duke University study recently found that blacks often believed that Latinos stole jobs, while Hispanics regarded African Americans as lazy and untrustworthy.

Others have suggested a more subtle dynamic. Rodolfo de la Garza, at Columbia University in New York, says that Hispanics have little need for the redemption that support for Mr Obama offers liberal whites. “Latinos,” he says, “have not been the ones persecuting blacks.”

Antonio Villaraigosa, the Los Angeles Mayor, who backs Mrs Clinton, is irritated by this talk of race. He points out that both he and one of his black predecessors, Tom Bradley, were elected with strong backing from both communities.

“Some people want to reduce this to a caricature of brown against black,” Mr Villaraigosa told The Times, “but this had everything to with perceptions of [Mrs Clinton's] track record.”

In New Mexico, the Governor, Bill Richardson, suggests that experience counts among voters craving to be treated as part of the majority. “Obama is a new face,” he said. “That's attractive to many people and risky to many others.”

Mrs Clinton’s Spanish-language advertisements are designed to reinforce her image as “our friend” — a longstanding advocate of reforms that would give legal rights to millions of undocumented workers.

Mr Obama says he is “aggressively” courting the Latino vote and has highlighted his own background as the son of a Kenyan immigrant. He supports plans for allowing illegals to acquire driver’s licences, a measure opposed, after some hesitation, by Mrs Clinton.

At campaign rallies he has supplemented his usual Motown music with Ricky Martin’s bilingual soccer anthem The Cup of Life, while Senator Edward Kennedy — revered among Hispanics — has sought converts for him in New Mexico and Eastern Los Angeles.

Maria Elena Durazo, a prominent Obama supporter in California, acknowledges that it is “an uphill battle for him”. Mrs Clinton is backed by the emblematic United Farmworkers of America, even though Mr Obama has adopted its slogan “Sí se puede” — “Yes we can” — as his own.

It was heard often at a rally at UCLA yesterday with Caroline Kennedy, Oprah Winfrey, Stevie Wonder and Michelle Obama. The only thing particularly Latino about the crowd of pumped-up thousands, however, was the Mexican wave they performed.

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