Puerto Rico's “second-class” American citizens will finally be given a voice this week in the contest for the Democratic presidential nomination, even though Barack Obama is acting as if he has already won it.

Hillary Clinton has spent the past three days storming across the Caribbean island, swapping her standard dark trouser suit for a bright pink tropical blouse and, on more than one occasion, allowing herself to be seen dancing. Yesterday she was joined by her husband, Bill, and their daughter, Chelsea, for a series of “conversations with Puerto Rican families”.

She has shrugged off the controversy over her remarks suggesting that the assassination of Robert Kennedy in 1968 meant that unforeseen events could still transform the race. Instead, Mrs Clinton tells crowds that by fighting on she has given them an historic chance to help to pick the next president. “If I had listened to those who have been talking in the last several months, we would not be having this campaign in Puerto Rico,” she told churchgoers.

Mr Obama, by contrast, made a more token visit to the island on Saturday before heading back for a sweep through Western states expected to be crucial in November's election. Yesterday he was in New Mexico, today he is scheduled to be in Nevada, tomorrow in Colorado.

As a US territory, Puerto Rico has a murky, much-disputed status, being more than a colony and less than a fully fledged state. Sunday's primary is regarded by many as an oddity, even an inconvenience, because the 2.3 million registered voters, whose language, culture and economy more closely resemble Latin America than any part of the mainland US, are not allowed to participate in presidential or congressional elections.

The Democratic party, doing its best to be inclusive, allows Puerto Rico to elect 55 delegates for the nominating convention but has never really considered the prospect of the primary counting for much. It is, perhaps, the equivalent of Gibraltar being given a say in the choice of the next British Labour Party leader.

Indeed, some of Mr Obama's supporters, if not his campaign, say it is wrong to include Puerto Rico in tallies of the Democratic popular vote. But Roberto Prats, the chairman of Puerto Rico's Democratic Party and himself a leading Clinton backer, said yesterday such people “need to be educated”.

Mr Prats said: “We're eager to seize this opportunity. We're gong to have a primary, we have followed all the rules and there is no way these votes will not be counted.”

Although Mrs Clinton knows she cannot catch her rival among elected delegates, she is eyeing hungrily the hundreds of thousands expected to go to the polls in Puerto Rico. Her campaign believes she can still beat Mr Obama in the popular vote, particularly if Saturday's meeting of the Democratic rules committee decides to reinstate the result from disputed primaries in Florida and Michigan.

She enjoys strong support on the island, where her long-standing appeal to Latinos is reinforced by her role as New York Senator, representing up to a million Puerto Rican migrants. In addition, if Mrs Clinton can run up her vote total on Sunday, it will at least give her more credibility in possible negotiations for the post of vice-presidential running mate.

Mr Prats predicted yesterday that the turnout would be high but he significantly downgraded previousforecasts of a seven-figure vote to about half a million. “Hillary will win by a sizeable margin,” he said, “and we are looking forward to proving the pundits wrong.”

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