If the victory in Puerto Rico turns out to be Clinton's 'last hurrah', then she made the most of it by campaigning in Puerto Rico with energy and confidence.
"It was the most fun I think I've ever had campaigning anywhere," she said. "I pledge to you that from day one of my presidency, I will work with all factions and with the Congress."
Senator Clinton spent far more time in Puerto Rico than did Barack Obama, and she was expected to win easily. However, the more tough races are coming up in Montana and South Dakota.
" She's working very hard to try to run up her popular vote tally so that she can make some kind of argument at the end of this campaign that she got more votes than Senator Obama," said Democratic strategist Michael Feldman.
Clinton already is making that argument in a new ad.
"Seventeen million Americans have voted for Hillary Clinton, more than for any primary candidate in history," the ad says.
Barack Obama was in South Dakota Sunday. His mood was upbeat, even though the news from Puerto Rico was not good. Outside the Corn Palace in Mitchell, South Dakota, Obama was gracious in defeat. Puerto Rico voted against him by as much as 2-to-1.
"I just got off the phone with Senator Clinton. She's going to win Puerto Rico, and I wanted to congratulate her for that," Obama said.
Obama can afford to be magnanimous because he now needs just over 50 more delegates to secure the Democratic nomination. He should clinch it in the coming week.
"I really think the party is going to come together after Tuesday's voting is over. I think we'll see a number of superdelegates declare their intentions, and then the math is going to become very, very clear," said Mark Mellman, a Democratic pollster.
Obama has scheduled his victory party for Tuesday in St. Paul, Minn., where the Republicans are holding their national convention over the summer.
Meanwhile, Republican John McCain did not campaign over the weekend.