Democrat Hillary Rodham Clinton won a decisive victory over Barack Obama here on Sunday in one of the last Democratic primaries in a presidential nominating contest that has mostly slipped from her once-formidable grasp.
The Associated Press declared Clinton the winner less than an hour after the polls closed. Early returns showed the former first lady was gaining more than 60% of the vote.
According to an AP analysis of the early returns, Clinton won at least 28 delegates of the 55 at stake in Puerto Rico while Obama won at least 14, with 13 still to be allocated. That brings the Illinois senator tantalizingly close to the 2,118 needed for the nomination.
Clinton campaigned even into Sunday in an apparent attempt to pick up as much of the popular vote as possible during the waning days of the primary calendar to try to demonstrate her vote-getting appeal to Democratic party figures.
Obama, speaking at a rally in Mitchell, S.D., late Sunday congratulated Clinton on her victory in Puerto Rico, calling her "an outstanding public servant."
He also said that supporters of both candidates would unite for the fall election, but made it clear that he expects to be the party's standardbearer.
"She is going to be a great asset when we go into November to make sure we defeat the Republicans, that I can promise you," Obama told the crowd.
The Clinton victory, while sizable, was largely symbolic. Puerto Rico, where the island's residents — all U.S. citizens — cannot vote in the November general election.
The win did demonstrate Clinton's strength among Hispanic voters, who have supported her over Obama in contests aleady held in states such as California, Arizona and Texas.
But the bid for the presidential nomination increasily has come down to the delegates, and the need to appeal to so-called superdelegates, the party leaders who are free to choose regardless results in primaries.
On Saturday, the Democratic Party's Rules and Bylaws Committee agreed to give disputed delegates from Florida and Michigan a half vote each at the party's nominating convention in Denver. The decision angered Clinton and did little to help her close the lead Obama has on delegates needed to clinch the nomination.
With the panel's decision, which took place on the eve of the Puerto Rico election, Obama had 2,052 delegates and Clinton had 1,877 delegates.
The Clinton campaign accepted the Florida decision, but objected to the terms of the Michigan settlement.
"This decision violates the bedrock principles of our democracy and our party," Clinton's campaign said in a statement by Harold Ickes and Tina Flournoy, two of her advisers. Ickes said on NBC's Meet the Press on Sunday that Clinton had reserved the right to take the fight to the party's credentials committee or even to the convention in Denver in August.
A spokesman for the Obama campaign said the Illinois senator could secure the nomination this week, perhaps as early as Tuesday, after the Montana and South Dakota contests.
"If not Tuesday, I think it will be fairly soon," Obama spokesman Robert Gibbs said Sunday on ABC's This Week.
The biggest remaining bloc of votes is made up of party leaders known as superdelegates who are free to choose regardless of results in primaries. Many had been reluctant to declare a preference until after completion of all the primaries and caucuses.