South Carolina restored Bush's front-runner credentials so badly shattered in New Hampshire. The defeat leaves McCain in need of a new bounce to keep his campaign alive.

The Texas governor pieced together his triumph the time-tested way. He ran strongest among staunch Republicans, the very conservative, abortion opponents, members of the religious right and Palmetto State natives.

More than half the voters said they preferred a candidate who was loyal to the Republican Party, and Bush won their support by an overwhelming margin of 4-1.

McCain, who stunned Bush with a double-digit victory in New Hampshire two weeks ago, ran best among independents, moderates and those who were not native to South Carolina.

The state was a pivot point for both men. Just ahead is a three-week string of primaries that will likely decide the winner in the nomination battle. Without momentum, McCain is at a disadvantage against Bush's 50-state organization.

McCain said that with a win in South Carolina, there'd be no stopping him -- and not many Republicans had the stomach for arguing with him.

Bush looked to South Carolina -- the first of several campaign firewalls he claims around the country -- to slow his rival, but also to steady the nerves of his supporters in Congress and elsewhere in the GOP establishment. Without naming names, he derided some of his supporters last week as weak-kneed for fearing his campaign was about to unravel.

South Carolinians have been here before, even if Bush and McCain have not. The state's GOP voters embraced George Bush in 1988 and 1992, after he had been scared in earlier contests. And it served as a Bob Dole firewall in 1996.

The balloting marked the culmination of a tough 18-day campaign, one in which Bush successfully co-opted McCain's message as a reformer of the political system by stressing his credentials as a "reformer with results."

Exit polls conducted for The Associated Press and the television networks showed about 23 percent of the voters said Bush was the real reformer in the race. McCain was chosen by 17 percent.

On the other hand, the same polls show that Bush benefitted from the perception among the voters that McCain had unfairly attacked him. Almost half the voters said McCain had unfairly attacked the Texas governor. Only one-third said Bush had attacked unfairly.

In retrospect, negative advertising seems to have been a key tactical issue, as well.

Angered by an attack on him by a veteran campaigning for Bush, McCain authorized negative commercials, including one that said the Texas governor twisted the truth like Bill Clinton. Then, when his internal polls showed support eroding, he ordered the ads stopped.

But that left Bush free to run all the negative commercials he wanted without risk of retaliation -- at the same time he complained that McCain had sullied his reputation by likening him to Clinton. "That's about as low a blow as you can give in a Republican primary," the governor said.

McCain's aides, a close-knit group, disagree on who advocated the first negative commercials and how sharply worded they should be -- a sign that the strategy was not as successful as they had hoped.

In victory, neither Bush nor his surrogates claimed the nomination was theirs. At the same time, Rep. Roy Blunt of Missouri, Bush's liaison to the House, said, "It will be hard for McCain to transition from this two-state strategy into a 50-state effort without a boost of energy like he got in New Hampshire."

Michigan votes in two days' time, the first of the classic general election swing states to hold a primary. That makes it a critical test of McCain's claim to be the more electable of the two contenders. And he's up against a different kind of firewall in the state, one erected by Gov. John Engler.

The South Carolina outcome had an immediate impact on Virginia, which votes on Feb. 29. It was not in McCain's original playbook _ that called for victories in New Hampshire, South Carolina and Michigan, followed by California on March 7. But he had a modest effort under way in the Old Dominion, with a large military and retired retired military population, and was ready to reevaluate his plans if South Carolina had gone his way. Instead, aides decided to shift resources to Washington, which votes the same day, and not make a serious play for Virginia's 56 delegates.