BARACK OBAMA and Hillary Clinton face off today in what could be the decisive contest of the Democratic presidential campaign as Pennsylvania becomes the last big state to hold a primary. Both candidates made last-minute appeals across the state as polls showed Mrs Clinton with a lead of about six points in a state she must win to keep her faltering candidacy alive.
Campaigning in Scranton yesterday, Mrs Clinton warned voters against taking "a leap of faith" on Mr Obama, promising to be a dependable champion if she returns to the White House.
She urged them: "Please, in the next 36 hours, do everything you can: convince people to go vote who say that they're not voting, take them to the polls, call your friends and neighbours, make the case for the kind of result that we desperately need in America again."
Mr Obama, who has outspent his rival in the state by a margin of more than two to one, admitted yesterday that he does not expect to win but hopes to limit Mrs Clinton's margin of victory.
"We have run a tough race here in Pennsylvania," he told a Pittsburgh radio station. "Senator Clinton obviously was heavily favoured. She was up by 20 points and we have just been trying to chip away and had a great time campaigning.
"I am not predicting a win. I am predicting it is going to be close and that we are going to do a lot better than people expect."
Today's primary follows the most heated campaigning of the entire primary season as Mr Obama has been forced on the defensive over controversial remarks by his former pastor and his own description of small-town Pennsylvanians as "bitter".
Neither controversy has given Mrs Clinton the breakthrough she hoped for, and even if she wins today she is unlikely to make a significant impact on Mr Obama's lead among the delegates who choose the Democratic nominee.
Tracking polls suggest, however, that recent controversies have damaged Mr Obama, and he has seen a 13-point national lead over Mrs Clinton disappear over the last week. Pennsylvania polls show Mr Obama winning more than 80 per cent of the African-American vote and with a comfortable lead in Philadelphia, where 35,000 people attended his biggest-ever rally last Friday.
Elsewhere in the state, particularly in the north and west, where voters are older, poorer and more conservative, Mrs Clinton is ahead and both campaigns have established formidable ground operations to mobilise supporters.
Mrs Clinton has the support of Pennsylvania's governor Ed Rendell, and of the mayors of Philadelphia and Pittsburgh, while Mr Obama's most prominent backer is the state's freshman senator Bob Casey.
A convincing victory today would allow Mrs Clinton to take her campaign on to North Carolina and Indiana on May 6th, in the hope that voters and Democratic delegates will take a second look at Mr Obama and pause before anointing him as the party's nominee.
Mr Obama has an almost insuperable lead among pledged delegates, he is ahead by 700,000 in the accumulated popular vote and senior party figures have been moving steadily in his direction.
He also enjoys an overwhelming financial advantage, with more than $40 million cash-in-hand at the start of April, while Mrs Clinton had $9 million - and $10 million in debts.
While the Democrats battle in Pennsylvania, Republican candidate John McCain has been raising funds and introducing himself to voters on a nationwide tour of what he described as the country's forgotten places. In Selma, Alabama, yesterday, Mr McCain attempted to reach out to African-American voters, although he acknowledged that it would be an uphill battle to gain their support in November.
"I have had long and varied experiences with people from all communities and all ethnic backgrounds in America," he said. "I am aware of the fact that there will be many people who will not vote for me but I'm going to be the president of all the people and I will work for all the people."