IMMIGRATION, THE issue which almost killed John McCain's candidacy before it began, is threatening his US presidential ambitions again. The gulf between Republican rhetoric and Hispanic expectations has never been wider. Somehow, though, he must walk a wire between the two.

Based on his voting record, McCain is as progressive on immigration as Barack Obama. He has consistently supported the creation of a path to citizenship for people who have entered the US illegally, in tandem with a guest worker programme. To many in his own party this "amnesty" is a dirty word.

In his re-election, George Bush won 40% of the Hispanic vote. McCain needs to match that, particularly in the south-west. In New Mexico, almost a third of the electorate is Spanish-speaking. In Nevada and Colorado the percentage is lower, but still potentially decisive. At the National Council of La Raza (NCLR), an influential Hispanic rights organisation, Obama stated flatly that "the Latino community holds the election in its hands".

McCain delivered his pitch to the NCLR the next day, reminding it that "at a moment of great difficulty in my campaign, when my critics said it would be political suicide for me to do so, I helped author with Senator Kennedy comprehensive immigration reform."

The McCain-Kennedy Bill, or the Secure America and Orderly Immigration Act, was never voted on in the Senate, partly because of the implacable opposition of homeland security hardliners, but also because it proved politically unpopular.

CNN anchor Lou Dobbs made illegal immigration his signature issue and scored the highest ratings on the network. The lesson learned by the Republicans was that in discussing the nation's porous borders, no talk is too tough.

Presidential debates were shaped by the agenda of Colorado congressman Tom Tancredo, who believes that every undocumented worker in America should be deported. Mitt Romney, a fellow contender for the Republican candidacy, described McCain's proposed legislation as "offensive" and attacked Rudy Giuliani for running a "sanctuary city" in New York.

By the Iowa caucus, McCain had realised his position on immigration was untenable. "I got the message," he told voters in Sheldon. "We have to do what's necessary to secure our border, and then we can move on to other aspects of the problem."

By formulating his policy this way - border first, reform second - McCain hopes to reassure conservatives without alienating Hispanic-Americans.

Presenting it to the two constituencies is a delicate business. When he told the National Association of Latino Elected and Appointed Officials that reform "will be my top priority yesterday, today and tomorrow," it caused outrage on conservative blogs.

Tancredo wrote McCain an open letter asking: "Are you planning to break a promise you made in February to postpone all other immigration reform legislation until we have first secured our borders?"

In Chicago, he addressed a closed meeting of Hispanic community leaders, unaware that one of them, Rosanna Pulido, was from the Minuteman Project, a controversial vigilante group which patrols the zone between the US and Mexico.

Pulido later told the Associated Press: "He's one John McCain in front of white Republicans. And he's a different John McCain in front of Hispanics I'm outraged that he would reach out to me as a Hispanic but not as a conservative."

Immigration ranks only fifth in the electoral concerns of Latino voters. In a Pew Hispanic Centre poll last year, 79% of people surveyed described it as a "very important" or "extremely important" issue, but put it behind education, healthcare, the economy and crime. Iraq was sixth.

McCain is presenting himself as a social conservative who has fought alongside Hispanic-Americans for his country. He often talks about refusing early release from a PoW camp in Vietnam because "my beloved friend Everett Alvarez, a brave American of Mexican descent, had been shot down years before I was".

A recent radio commercial featured his Naval Academy room-mate, Frank Gamboa, telling listeners in Spanish that McCain "shares our conservative values and faith in God" and "knows that family is the most important thing we have and that we value hard work".

During the Democratic primaries, Obama sometimes found it difficult to win Hispanic votes. But that was against Hillary Clinton, who had spent decades fostering links with the community. The Clintons are still the strongest brand in Hispanic-American politics.

The Republican Party brand, traditionally popular with Cubans but few other Latinos, has been further compromised by the openly xenophobic tone of the immigration debate.

In the latest hypothetical presidential election match-up, carried out by CBS and the New York Times, Obama leads McCain among Hispanic voters by 62% to 23%. McCain must do better than that to avoid being swept away in the southwest. He is the only Republican who could close the gap, but he will have one hand tied behind his back by Tom Tancredo.