John McCain clinched the Republican presidential nomination on Tuesday and Democrat Hillary Clinton won a crucial showdown with rival Barack Obama in Ohio to breathe new life into her campaign and prolong the Democratic race.
McCain's four big victories in Vermont, Ohio, Texas and Rhode Island drove his last major rival, former Arkansas Gov. Mike Huckabee, out of the race and gave McCain more than the 1,191 delegates needed to win the nomination.
President George W. Bush will greet the Arizona senator at the White House on Wednesday and back his campaign.
"I am very pleased to note that tonight, my friends, we have won enough delegates to claim with confidence, humility and a sense of great responsibility that I will be the Republican nominee for president of the United States," McCain, 71, told supporters in Dallas.
Ohio and Texas loomed large Tuesday for Democrats Barack Obama and Hillary Rodham Clinton, with excrutiatingly close primaries in both states determining the final chapter of a mesmerizing presidential contest.
After 11 straight losses to Obama, Clinton mustered a win in tiny Rhode Island while Vermont delivered an overwhelming victory to Obama. But it was contests in the southwest and in the heartland that would set the direction for the campaign to come.
Mike Huckabee bowed to reality Tuesday and out of the Republican presidential race. "We kept the faith," he told his end-of-the-road rally Tuesday after John McCain clinched the nomination. "I'd rather lose an election than lose the principles that got me into politics in the first place."
The genial conservative went out as he had campaigned all along, with a quip: "It's time for us to hit the reset button."
John McCain's last-man-standing strategy prevailed. Now, on to the general election and the hurdles that come with it.
"I do not underestimate the significance nor the size of the challenge," the Republican nominee-in-waiting told the Associated Press on Tuesday, looking to the next chapter of his presidential quest.
A significant challenge is right.
Hillary Rodham Clinton showed renewed strength Tuesday in Texas and Ohio among whites and working-class voters who had begun deserting her in recent contests, early results from exit polls in the states showed.
With her back against the wall in a pair of contests that seemed virtually must-win, the New York senator seemed to be limiting Barack Obama to groups that have supported his candidacy from the start of this year's Democratic presidential contest.
John McCain secured the Republican presidential nomination as the ultimate survivor -- winning it eight years after his first failed attempt and decades after cheating death in the Vietnam War.
Easy to laugh and easy to anger, McCain carries with him the scars of battle in both armed conflict as a naval pilot and in the political wars of Washington as a U.S. senator from Arizona.
NBC News has declared Hillary Rodham Clinton as the winner of the Democratic primary in Ohio.
With just over 50 percent of the votes counted, Clinton has 57 percent of the vote compared with 41 percent for Barack Obama.
Barack Obama and Hillary Rodham Clinton split a pair of New England primaries Tuesday night and vied for bigger prizes in Ohio and Texas in a riveting Democratic presidential race. Arizona Sen. John McCain, an unflinching supporter of the war in Iraq, clinched the Republican nomination.
"We are in Iraq and our most vital security interests are involved there," said McCain at a victory celebration nearly a decade in the making.
Obama won Vermont's Democratic primary, gaining nearly 60 percent of the vote for a 12th straight victory over the former first lady.
Hillary Clinton has been declared the winner of the Democratic primary in Rhode Island giving her one race out of four with contests in Ohio and Texas still undecided.
With eight percent of the vote counted, Clinton had 53 percent of the vote, compared to 45 percent for Barack Obama.
Obama was declared the winner in Vermont earlier in the evening. The races in Ohio and Texas are still too close to call.
With Arizona Sen. John McCain clinching the Republican nomination, former Arizona Gov. Mike Huckabee dropped out of the race Tuesday night, saying he ran a good race and did not want to call it quits until the race was officially over.
Huckabee spoke to supporters shortly after McCain officially clinched the nomination, surpassing the required 1,191 votes needed for the Republican nomination.
Huckabee compared his race to a stalled computer, saying it was "time to hit the reset button."