Hillary Clinton and Barack Obama embarked Thursday on a five-day march toward the pivotal Pennsylvania primary, as the endgame opens in the Democratic White House tussle.
Campaign aides for each White House hopeful claimed victory after the senators clashed in a tense and grim debate here late Wednesday, both arguing their candidate was best placed to beat Republican John McCain in November.
Obama was already looking past next Tuesday's Pennsylvania primary to a knockout win in North Carolina, which along with Indiana votes on May 6 in the closing stages of the arduous nominating epic.
"North Carolina is going to be critically important. If we can win in North Carolina, I think we can wrap up this nomination," he said at a campaign stop in the southern state before heading back to Pennsylvania.
"And if we can win this nomination then I think we can beat John McCain," the Illinois senator said.
All three contenders got a chance to burnish their foreign policy credentials in Washington talks with Britain's visiting Prime Minister, Gordon Brown, who said the historic Anglo-US alliance would remain in safe hands.
"What I was convinced of, after talking to each of them ... is that the relationship between America and Britain will remain strong, remain steadfast," Brown told a news conference with President George W. Bush.
In the run-up to Tuesday's primary, Obama was blanketing the airwaves in the gritty northeastern state with millions of dollars in campaign advertising.
He was also due to launch Friday a trek through Pennsylvania by road, rail and air, even as his campaign downplayed expectations for him in a state where Clinton is favored to win.
Obama lashed the format of the debate on ABC television, after he was put on the defensive over his fiery former pastor, comments that some working Americans were "bitter" and his reluctance to wear a US flag lapel pin.
Decrying the moderators, he said it was "45 minutes before we heard about health care, 45 minutes before we heard about Iraq, 45 minutes before we heard about jobs, 45 minutes before we heard about gas (gasoline) prices."
Clinton was also planning to criss-cross the state, the gateway to the intense closing weeks of the punishing Democratic race, which has now lasted 15 months.
"We feel good about it, if Senator Obama is unable to win Pennsylvania, it will show once again he is having problems winning the big swing states," Clinton communications czar Howard Wolfson told MSNBC television.
Wolfson told reporters that Obama had a "very bad night" in the debate, and failed to adequately answer questions about his character that Republicans would use against him if he emerges as the Democratic nominee.
Polls show Clinton with around a six-point lead in Pennsylvania, short of the blowout she would need to seriously dent Obama's lead in elected delegates, going into the next two primaries in Indiana and North Carolina.
The former first lady used the debate to hammer Obama on his character and his feel for American values as she tried to ignite a comeback bid, rebuking her rival over his remark last week that blue-collar voters felt "bitter."
Clinton was also called to account for her exaggerated account of a trip to Bosnia, which she had claimed was threatened by sniper fire -- comments contradicted by recently aired video footage.
Obama said he had "mangled" his words when arguing in San Francisco that working-class Americans cling to guns and religion out of anger at their economic plight. But he tried to navigate out of the drama.
"Yes, people are frustrated and angry about it, but what we're seeing in this election is the opportunity to break through that frustration," Obama said.
Despite their disagreements, both candidates insisted that whoever wins the nomination would beat McCain in November.
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