Sen. Barack Obama went on the attack Wednesday, signalling a possible shift in campaign tactics after Sen. Hillary Clinton won three primaries.
When asked whether Clinton had more experience to deal with major issues as president, Obama took aim at her record.
"Was she handling crises during this period of time? My sense is the answer is no," he told reporters.
Meanwhile, the dust is still settling in the Texas caucuses, with ongoing results showing Obama edging ahead of Clinton, who won the state's primary Tuesday night.
With roughly 40 per cent of the caucuses' results counted, Obama had 56 per cent support while Clinton had 44 per cent.
Clinton secured three much-needed wins Tuesday night, including a major victory in Ohio, putting a halt to Obama's 12-state winning streak and reviving her campaign for the Democratic nomination.
"You know what they say, as Ohio goes so goes the nation," she told supporters. "Well, this nation is coming back and so is this campaign."
Late returns indicate that she may have emerged with a net gain of about 12 delegates, with a dozen yet to be awarded, according to an Associated Press tally.
Obama's delegate lead is roughly the same as it was before Tuesday's contests, although he only won Vermont. Clinton won Ohio, Rhode Island and the Texas primary.
While counts vary in media reports, it appears that Obama has more than a 100-delegate lead over Clinton. The AP late Wednesday afternoon had Obama with 1,562 delegates and Clinton with 1,461.
The first candidate to secure 2,025 delegate votes will win the party's nomination in upcoming primaries.
Coming up on Saturday, the Wyoming primary has 12 delegates. Following that, Mississippi has 33 next week, and Pennsylvania offers 158 on April 22, the largest remaining prize.
Speaking on CBS's "The Early Show," Clinton suggested she may be open to sharing a ticket with Obama.
"That may be where this is headed, but of course we have to decide who is on the top of the ticket. I think the people of Ohio very clearly said that it should be me," she said.
After his hopes of knocking Clinton out of the race went unfulfilled, Obama said he would continue to fight on, but gave credit to Clinton as an opponent who "just keeps on ticking."
A shift in the winds
Many observers had predicted there would be a massive campaign to get Clinton out of the Democratic race if she didn't regain serious ground in Tuesday's voting.
Presidential historian and author Allan J. Lichtman said there appears to have been a shift in the campaign winds.
"You've got two very strong Democratic candidates, each with a very powerful metaphor. Of course the Obama metaphor is, 'I'm something new, I'm going to change the old corrupt ways of Washington.' And the Clinton metaphor is, 'I'm ready, I'm prepared, I'm a fighter.' First the Obama metaphor was prevailing, now the Clinton metaphor seems to be coming to the fore," Lichtman told CTV's Canada AM.
However, he said it will still be tough, mathematically, for Clinton to surpass Obama's lead.
"She wants to string together the kind of wins that Obama had in February," Lichtman said.
CTV's Joy Malbon said the battle could continue for some time if the race remains close.
"It's all about math and momentum," she told Canada AM. "She can now claim she's got the momentum by snapping his winning streak, but he's got the math with more than 130 pledged delegates. So this rodeo is going to go on and on."
Bush vows to help McCain
While the Democrats looked ahead Wednesday to future primaries, U.S. President George Bush invited Republican nominee John McCain to the White House for an official endorsement.
He said the Arizona senator has what it takes to keep Americans safe.
McCain sealed his bid for the Republican presidential nomination on Tuesday, receiving the support of the 1,191 delegates he needed to put him over the top. That ended the campaign of former Arkansas governor Mike Huckabee, his last real challenger.
Addressing reporters in the White House's Rose Garden on Wednesday, Bush described McCain -- a bitter rival for the Republican presidential nomination in 2000 -- as a man of character and courage.
"But he's not going to change when it comes to taking on the enemy. He understands this is a dangerous world, and I understand we better have steadfast leadership who's got the courage and determination to pursue this enemy," he said.
"This country better have someone in the Oval Office who understands the stakes. John McCain understands those stakes."
McCain supports the war in Iraq and steadfastly campaigned for the nomination as a national security candidate despite the declining U.S. economy.
McCain said he hoped Bush -- whose approval ratings are very low -- will campaign with him as much as his schedule will allow.
As the last Republican candidate standing, McCain can begin preparing his party for a presidential run.
In terms of picking a vice-president, Bush didn't have much advice, even given that McCain will be facing either a woman or an African-American -- either of which would be unprecedented in American political history.
"People don't vote for vice-presidents. They vote for who gets to sit inside that Oval Office and makes decisions on how to protect the country and keep taxes low and have a culture that respects the dignity of every human being," Bush said.
With a report by CTV's Washington Bureau Chief Tom Clark and files from The Associated Press
