Barack Obama appeared to be just days away from becoming the first black presidential nominee of a major US political party today.
A landslide primary win by Hillary Clinton did little to revive her failing campaign.
The victory yesterday in Puerto Rico will not keep Mr Obama from winning the nomination, but his string of defeats at the end of the primary campaign, such in West Virginia and Kentucky, have highlighted his weaknesses among white working-class and Hispanic voters that could undermine his hopes of defeating Republican John McCain.
Mr Obama is 45 delegates short of the 2,118 needed to win the nomination. Aides predicted he could clinch the nomination as early as tomorrow, as Montana and South Dakota mark the end of a bitter and hard-fought primary season.
The former first lady enters this week with a strategy not only to win over undecided superdelegates but to peel away Mr Obama’s support from those party leaders and elected officials who already have committed to back him for the nomination.
“One thing about superdelegates is that they can change their minds,” she said yesterday.
Mr Obama displays no signs of worry, looking toward the November general election against Mr McCain. Some of Mrs Clinton’s own backers are saying the time is near for her to fall in behind him.
Mrs Clinton won a lopsided but largely symbolic victory in Puerto Rico – a Caribbean US territory that votes in the primaries but does not participate in the presidential general election.
With 31 delegates at stake tomorrow, Mr Obama could close the gap further and cue undecided superdelegates to come to his side. He picked up two more superdelgates today.
Mr Obama, campaigning in Mitchell, South Dakota, confidently predicted Mrs Clinton “is going to be a great asset when we go into November.”
“Whatever differences Senator Mrs Clinton and I may have, those differences pale in comparison to the other side,” he said.
He has made up most of the ground he lost on Saturday when the national party’s rules committee agreed to reinstate delegates from Michigan and Florida.
Mrs Clinton’s decision to battle on, if prolonged, is not likely to sit well with party leaders and some of her own supporters. Democrats House Speaker Nancy Pelosi and Senate Majority Leader Harry Reid have both called on the contest to end shortly after the final primaries.
Tom Vilsack, the former Iowa governor and a national co-chairman of Mrs Clinton’s campaign, said yesterday: “It does appear to be pretty clear that Senator Obama is going to be the nominee. After Tuesday’s contests, she needs to acknowledge that he’s going to be the nominee and quickly get behind him.”