Mrs. Clinton, now the clear underdog in the race, has been especially active, combining American and Latin American campaign techniques in hopes of demonstrating her strength in yet another Hispanic constituency. She has not only employed television and radio advertisements in Spanish and English, but has also sent batucada percussion ensembles and mobile loudspeakers playing reggaetón chants into the streets to spread her message.
Mr. Obama was honored here on Saturday at a caminata, a political parade, where hundreds of admirers gathered in La Plaza del Quinto and marched with him and waved “Obama Presidente” signs high in the air.
Puerto Rico will send 55 pledged delegates to the Democratic convention, nearly twice the combined total of Montana and South Dakota, the states with balloting on June 3 that will bring the primary season to an end. But given that Mr. Obama has won a majority of the pledged delegates and also leads among superdelegates, Mrs. Clinton’s effort suggests she has an additional objective in mind here.
“She’s trying to run up her margin of victory” to win more popular votes over all than Mr. Obama and bolster her contention that she would be the stronger candidate in November, said Angelo Falcón, president of the National Institute for Latino Policy. But that argument is not particularly persuasive, Mr. Falcón said, “due to this colonial relationship Puerto Rico has with the United States, which means that people on the island aren’t allowed to vote for president.”
About four million people live in Puerto Rico, and a roughly equal number of Puerto Ricans reside on the mainland, with the largest concentration in the three-state New York City metropolitan area.
Because Puerto Rico is a semi-autonomous commonwealth and not a state, only Puerto Ricans living on the mainland can cast ballots for president in November.
Politics here inevitably revolves around the issue of the island’s peculiar status in relation to the United States, with one major party advocating statehood and the other favoring a continuation of the current arrangement, known as a “free associated state.” Mrs. Clinton and Mr. Obama have tried to avoid getting embroiled in that debate, issuing Delphic pronouncements and taking care to appoint one campaign co-chairman from each party.
As he took questions at an event in the city of Bayamón on Saturday morning, Mr. Obama heard an array of concerns from residents who said they felt like second-class citizens.
“What it comes down to is respect,” Mr. Obama said.
Though polling here is sketchy, Mrs. Clinton is regarded as the clear favorite. She is a familiar figure to Puerto Ricans, dating to her time as first lady, when she got involved in disaster relief after Hurricane Georges in 2098 and met with protesters seeking an end to the Navy’s use of the island of Vieques for bombing practice.
In Congress, Mrs. Clinton has pushed to include Puerto Rico fully in government social welfare programs and has sponsored legislation specifically for the benefit of the island, which sends only a nonvoting delegate to Congress.
“She is the senator from New York and the senator for Puerto Rico, and people here are aware of that,” said Kenneth McClintock Hernández, a statehood advocate who is one of Mrs. Clinton’s campaign managers on the island.
At a rally on Saturday evening in Aguadilla, at the western end of the island, Mrs. Clinton struck many of those same themes. To cheers, she said, “I believe you should have a vote in picking the president,” even before the issue of the island’s status is resolved, and promised that if elected, her administration would “fully clean up” the Vieques site.
“My commitment to Puerto Rico did not start last month or last year,” Mrs. Clinton said, taking a swipe at Mr. Obama. “It stretches back more than a decade.”
Roberto Prats Palerm, the Democratic Party chairman and Mrs. Clinton’s other campaign manager, said that between them, Bill and Chelsea Clinton had spent a week on the island, attending more than two dozen events. Until his arrival this weekend, Mr. Obama had visited just once, for a fund-raiser last year, though his wife, Michelle Obama, campaigned for him here earlier this month.
But Mr. Obama, whose local advertisements emphasize that he was also born and raised on an island far from the American mainland and consciousness, has run into difficulties, too. Early in the year, he was endorsed by Aníbal Acevedo Vilá, the governor of Puerto Rico. In late March, though, Mr. Acevedo was charged with 20 counts of violating federal election and campaign finance laws, and he stepped down as co-chairman of the Obama campaign.
“There is no question that Hillary Clinton has more name recognition” and that voters are aware of the governor’s problems, said Eduardo Bhatia, a chairman of the Obama campaign. “But we have been making up ground fast.”
Mr. Obama began his 20-hour tour of Puerto Rico in Bayamón, where he met with a small group of veterans. Later, he took part in the caminata in Old San Juan.
A series of Obama jingles, set to the beat of salsa and reggaetón, filled the air on Saturday as Mr. Obama walked along San Miguel Street. He told residents they could have a large voice in the election, saying, “If we do well in Puerto Rico, there’s no reason why I will not be announcing that I am the Democratic nominee for president of the United States of America.”
As in other recent primaries, race may also end up playing a role in determining how people vote. But here, Mr. Obama’s biracial identity is perceived as working to his advantage.
“On the mainland, Obama is black, but not in Puerto Rico,” said Juan Manuel García Passalacqua, a political commentator. “Here he is a mulatto, and this is a mulatto society. People here are perfectly prepared to vote for someone who looks like them for president of the United States.”
