That gives each man a different claim to take into the multistate competition in the weeks ahead -- McCain that his message of reform makes him better positioned to lead the GOP to victory this fall, and Bush arguing that Democrats are making mischief and will return to their own party in November.

Interviews with voters leaving their polling places in Michigan indicated that Republicans accounted for slightly less than half the ballots cast, and that Bush won them overwhelmingly. Independents accounted for roughly a third of the votes, and McCain ran as well with them as Bush did among Republicans. Democrats accounted for nearly 20 percent of the vote, and McCain was the overwhelming winner among this group.

"We've never seen a candidate like John McCain who went out to rent Democrats for a day," third-term Michigan Gov. John Engler, a Bush supporter, argued as the results were tabulated.

"John McCain isn't party building, he's party borrowing and there's a big difference," he said. Bush himself asked Republicans in the runup to the primary not to allow Democrats to dictate their choice.

McCain's surrogates and staff argued the other side, buttressed by a CNN-USA Today-Gallup poll released earlier in the day that showed McCain trumping Gore 59 percent to 35 percent in a hypothetical fall matchup.

"I want to make a special plea tonight to my fellow Republican," the Arizona senator said after the votes were counted. "I am a proud Reagan conservative," he added, mentioning his commitment to the military and his opposition to abortion. "Don't fear this campaign, my fellow Republicans. Join it, Join it."

Rick Davis, McCain's campaign manager, said the Arizona senator is demonstrating on a national scale the very cross-party appeal that Bush has shown in Texas and hopes to ride to the White House.

"It is Al Gore's worst nightmare," argued Davis. "John McCain's creating a new majority tonight. He showed some of his ability to do that in New Hampshire and here in one of the key states for the fall."

McCain's Michigan victory was critical to him. It was the first of the industrial states to vote, one of a number of swing states that will be pivotal to the general election in November.

In terms of the nominating campaign, his own aides said in advance he was in trouble if he lost in Michigan on the heels of his drubbing in South Carolina last Saturday.

McCain's prospects are now refreshed -- he also won Tuesday's GOP primary at home in Arizona -- and even before the votes were counted he and Bush were pointing toward next week's primaries in Washington state and Virginia.

McCain leads in the polls in Washington, and Bush in Virginia.

Those elections will set the stage for March 7, when 13 states hold primaries and caucuses and select 613 delegates to the Republican National Convention.

The primary rules governing whether independents can vote vary from state to state, something Bush and McCain must factor into their decisions about how to spend their time and money.

The pattern the exit polls found in Michigan first emerged in New Hampshire, site of the first primary Feb. 1. There, McCain, fueled by his call for government reform, won by 18 points despite running behind Bush among Republicans. Independents and Democrats accounted for 44 percent of the vote that night, and McCain won them handily.

Bush bounced back more than two weeks later in South Carolina, where the GOP faithful turned out in large numbers. They accounted for 61 percent of the primary vote, and allowed the Texas governor to swamp McCain.

That made Michigan round three in the primary campaign, as McCain said over and over in the runup to Tuesday's vote. This time, the exit polls said self-identified Republicans accounted for 47 percent of the vote -- well below the number only three days earlier in South Carolina.

Bush won two-thirds of their votes, roughly the same as in South Carolina.

But McCain defeated Bush by almost as big a margin among independents, who accounted for roughly a third of the vote, and by an even bigger margin among Democrats who cast an estimated 20 percent of the vote.

As the vote rolled in, Davis predicted that "soon the Republican party and its organizations will see that the best chance for maintaining majorities in the House and Senate and the governorships" lie with a McCain candidacy.