Perhaps it had to happen sooner or later: a Democratic presidential primary where voters just don't care.

It's happening later. After an extended season of sizzling competition and swollen turnout in state after state, it's Puerto Rico's turn, and the territory is showing little interest in what's left of the contest between Barack Obama and Hillary Rodham Clinton.

Local elections routinely attract 80 percent of voters. And the Democratic primary is open to all registered voters of whatever party, because Puerto Rico doesn't register voters by party. Nevertheless, electoral officials predict fewer than 25 percent of the 2.3 million registered voters will turn out for Sunday's primary.

This, despite the sizable prize of 55 delegates at stake, more than are offered in Montana and South Dakota combined in the last two primaries of the year, on Tuesday.

Islanders typically are reluctant to become entangled in mainland politics and now that most of the suspense is gone, it's questionable whether the forecast for 500,000 Puerto Ricans to vote will hold up.

"Traditionally people in Puerto Rico see the primaries as something far removed from their political reality," said Angel Rosa, a political science professor at the University of Puerto Rico at Mayaguez. "They don't see this primary as any kind of opportunity to send a message to the United States."

Obama and Clinton have both visited Puerto Rico over the last month in the hunt for the Caribbean island's delegates, but their rallies have failed to attract crowds of more than a few hundred.

Clinton has been outpolling Obama 2-1 with Hispanic voters, possibly giving her an advantage Sunday. But Obama is close to claiming the Democratic nomination regardless.

Puerto Rico's independence party, which polls at less than 5 percent in local elections, has called for supporters to boycott the primary because Puerto Ricans cannot vote in November's general election. Some members of mainstream parties also oppose the election.

Charlie Hernandez, a lawmaker from the governor's party that favors maintaining the island's commonwealth affiliation with the U.S., said the island has traditionally asked Washington to stay out of its business and should sit out the U.S. election.

"I think there are other ways to influence Washington without converting Puerto Rico into an appendage of North American politics," he said.

With enthusiasm flagging, coordinators of both campaigns have described the candidates in the context of the perennial issue that stirs political passions _ the unsettled relationship to the U.S., which seized Puerto Rico from Spain in 1898.

Clinton and Obama each have support from individual leaders of the two major parties _ the Popular Democratic Party, which favors the status quo, and the New Progressive Party, which wants Puerto Rico to become the 51st American state.

Both candidates have said that only Puerto Rico should decide its political status.

But Pedro Pierluisi, Obama's local co-chairman and a member of the statehood party, issued a statement Thursday that said the Illinois senator believes the U.S. is ready to accept Puerto Rico as a Hispanic state in the union if that's what islanders want.

Also Thursday, several officials with the governing party said Clinton recognizes that maintaining the current status is a valid option.

The primary will cost the island's government about $2.5 million, said Ramon Gomez, president of the elections commission.

One lawmaker said the price tag would have been reason enough to skip the primary.

"There are other priorities in education, health and public security," said Rep. Luis Vega Ramos of the Popular Democratic Party.

In the final contests, Montana has 16 delegates and South Dakota has 15.

Republicans placed less value than Democrats did on Puerto Rico, assigning 20 delegates in their February caucuses in the territory.

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Associated Press writer Manuel Ernesto Rivera contributed to this story.