Puerto Rico gave Sen. Hillary Rodham Clinton a victory over Sen. Barack Obama on Sunday, but she now faces an even bigger hurdle: stopping him from wrapping up the Democratic presidential nomination.

With all of the island's precincts reporting, Clinton captured 68 percent of the vote to Obama's 32 percent. In terms of delegates, it was a decisive victory for Clinton, who won 38 of the territory's 55 pledged delegates, leaving 17 for Obama.

In her victory speech to supporters in San Juan, Clinton continued to emphasize that she is the best candidate to lead the Democrats in the fall campaign. "We have what it takes to get the 270 electoral votes necessary to win the White House," said Clinton. "And the majority of voters know who is ready on day one to serve as our president."

Clinton went on to predict that neither she nor Obama would win a sufficient number of delegates in the last two remaining primaries on June 3, Montana and South Dakota, to clinch the nomination and that the party's uncommitted superdelegates will have to decide its outcome. Speaking to the superdelegates, she asked them to consider which candidate "represents the will of the people who voted" in the primaries, which candidate "is best able to lead to us victory in November" and which one "is best able to lead" in a time of "unprecedented challenges at home and abroad."

Either Obama or Clinton will need the votes of superdelegates to go over the top. Montana has only 16 pledged delegates at stake in its primary and South Dakota only 15. Montana has an open primary where any voter may participate, a system that has tended to favor Obama. South Dakota's primary is limited to registered Democrats, which could favor Clinton.

But on Saturday some of those very same superdelegates dealt Clinton a setback in her long-shot attempt to wrestle the Democratic nomination away from the front-runner Obama. Meeting in Washington, D.C., the Rules and Bylaws Committee of the Democratic National Committee voted to provide half-votes for delegates from Florida and Michigan, which had previously been stripped of all their convention seats for holding primaries earlier than permitted under party rules. Clinton, who won both contests, had supported full seating for the two states' delegations.

Moreover, because Obama had withdrawn his name from Michigan's primary, the committee decided to allocate the delegates according to a deal worked out by Democratic leaders in the state rather than by the results of the primary. That ruling had the net effect of taking away four delegates from Clinton's total and giving them to Obama, along with all the state's uncommitted delegates. The principle supporter of the deal, Michigan Sen. Carl Levin, said that the compromise had been reached with input from local supporters of both presidential contenders.

Nevertheless, the Clinton campaign strongly objected to the Michigan compromise, and Clinton herself told reporters on her campaign plane as it departed Puerto Rico that she reserved the right to bring a challenge to the DNC decision before the convention's credentials committee. "We'll get to that in due time, to consider whether we will or not," said Clinton. She declined to elaborate on what factors might weigh into that decision.

Clinton has been described by those close to her as having a realistic view about the long odds she faces in overtaking Obama. CNN estimates that he is only 48 delegates away from the 2,118 that are now needed to claim the nomination. But a senior Clinton campaign official yesterday described her as in a "fighting spirit." The official added that the Obama campaign and its supporters were "stupid" for not allowing Clinton the 73 Michigan delegates primary results would have dictated: "For four delegates, they kept the issue alive."

There was little surprise in Clinton's huge victory in Puerto Rico, given the solid support she has received from Latino voters in previous Democratic primaries. According to an exit poll conducted by Edison Media Research and Mitofsky International for CNN, Clinton handily won nearly every demographic and political group within the primary electorate -- young and old, male and female, college graduates and nongraduates.

Obama's only advantage came among voters who described themselves as members of the Popular Democratic Party (PPD), which supports enhanced commonwealth status for Puerto Rico. He narrowly carried that group with 52 percent to Clinton's 48 percent. Obama had been endorsed by PPD member and Puerto Rico Gov. Anibal Acevedo Vila. But Acevedo is under federal indictment for illegal campaign fundraising, and the cloud over him could have dampened the turnout of his party's rank-and-file for Obama.

The CNN exit poll found that only 36 percent of the primary voters described themselves as PPD supporters, compared with 57 percent who were affiliated with the New Progressive Party (PNP), which supports statehood for Puerto Rico. Among that group, a whopping 83 percent said they voted for Clinton.

Clinton had been endorsed by PNP party leader Pedro Rossello and former PNP Gov. Carlos Romero Barcelo. Neither Clinton nor Obama took a clear stand on backing statehood for Puerto Rico, but the exit poll found that those primary voters who supported that step overwhelmingly backed Clinton -- who took 81 percent of such voters -- while those who backed commonwealth status split 50-50 between the two candidates.

In her victory speech, Clinton said, "I hope by my second term, regardless of what the people of Puerto Rico decide about the status option you prefer, you too will be able to vote for the next president of the United States."

The only disappointment for the Clinton camp was in the size of the primary's turnout. Puerto Rico has more than 2.3 million registered voters, and in the 2004 general election, 82 percent cast ballots. Yet only 384,578 Puerto Ricans participated in Sunday's primary. Given the margin of her victory, a larger turnout would have strengthened Clinton's claim to be the popular vote leader in the primaries.

But Clinton seemed undeterred in her long odds and the late hour of the Democratic nominating contest. "It's not over 'til the votes are cast," said Clinton on her campaign plane, leaving unstated whether she meant the end of the primary balloting on June 3 or the roll call of the party convention in Denver in August. "It's not over 'til there's actually a tally that gets somebody the nomination."

NBC/National Journal campaign reporter Mike Memoli contributed to this report.