John McCain took a huge step yesterday down the road to the Republican presidential nomination, capturing an impressive array of primaries and piling up delegates across the country.

McCain won the winner-take-all contests in Arizona, Connecticut, Delaware, Missouri, New Jersey, New York and Oklahoma. He also prevailed in Illinois and in California, the big prize of Super Tuesday.

His only disappointment was that he came up a bit short of a national sweep, dropping five Southern and border states to Mike Huckabee and six other states, mostly in the West, to Mitt Romney.

And the senator from Arizona emerged with unresolved problems on his right flank, as he tries to persuade conservative opinion leaders that they have little to fear from his maverick tendencies and willingness to work with Democrats.

"Tonight, I think we must get used to the idea that we are the Republican Party front-runner for the nomination," McCain said at a rally in Phoenix. "I don't really mind it one bit."

McCain registered his best performances in places that traditionally have been hard for Republicans to carry in general elections, notably California and New York. He did less well in states that are part of the GOP base.

The surprise in the results was the revival of the Huckabee campaign. The former governor of Arkansas did particularly well among social conservatives in the South, even though the Republican race has been framed recently as exclusively a McCain-Romney affair.

"In the last few days, a lot of people have been trying to say this is a two-man race," Huckabee told his election-night party in Little Rock. "You know what? It is, and we're in it."

Huckabee's resilience was a source of great frustration to Romney, foiling his attempt to unify conservatives behind his own candidacy.

But Romney, who campaigned frenetically across the South on Monday, sounded upbeat when he spoke to his supporters in Boston.

"One thing is clear," the former Massachusetts governor said. "We're going to keep on battling. We're going to go all the way to the convention."

Underlining the challenge facing McCain in trying to hold together the coalition that elected Ronald Reagan and George W. Bush was the statement issued yesterday by James Dobson, a leading social conservative:

"I am convinced Sen. McCain is not a conservative, and in fact, has gone out of his way to stick his thumb in the eyes of those who are," said Dobson, who heads Focus on the Family, a conservative Christian group. "I cannot, and will not, vote for Sen. John McCain, as a matter of conscience."

In exit polls yesterday, only 49 percent of McCain voters described themselves as conservative, compared with 80 percent of Romney voters and 75 percent of Huckabee voters.

Yesterday, the Republican candidates, including Texas Rep. Ron Paul, had 1,023 delegates at stake in 15 primaries, five caucuses and a state convention in West Virginia.

For McCain, getting this far was a remarkable accomplishment, considering that he appeared on the verge of dropping out last summer.

At the time, his campaign was plagued by overspending, by infighting among his aides, by his outspoken support for the war in Iraq, and by his support for an immigration-reform package that conservatives viewed as offering amnesty to people living in the country illegally.

A British journalist wrote at the time: "If John McCain becomes president, it will be the greatest comeback since Lazarus." But McCain hung around, and events started breaking his way.

The surge strategy in Iraq, which he'd advocated, started producing results. Other Republican candidates, including former Tennessee Sen. Fred Thompson and former New York Mayor Rudy Giuliani, failed to catch fire with the voters.

McCain bet his campaign on the New Hampshire primary, which he had won in 2000, and the bet paid off with a repeat victory.

Then, with Romney and Huckabee siphoning conservative votes from each other, McCain edged Huckabee in South Carolina on Jan. 19 and beat Romney by a convincing margin in Florida on Jan. 29.

Conservative leaders, frustrated with McCain's rise and sensing there might be a majority that could be pulled together to stop him, blasted him in the week leading up to Super Tuesday and rallied behind Romney.

At the West Virginia party convention in Charleston yesterday, Romney asked: "Are we going to put a true conservative in the house that Ronald Reagan built, or are we going to take a left turn?"

McCain's campaign aired a new anti-Romney commercial Monday night, challenging Romney's claim to be a Reagan Republican. The ad noted that Romney voted in the Democratic presidential primary in 1992 and failed to embrace the Reagan record during a Senate race in Massachusetts two years later.

"Mitt Romney was against Ronald Reagan before he was for him," the announcer said. "If we can't trust Mitt Romney on Ronald Reagan, how can we trust him to lead America?"

Romney and Huckabee were sparring as well.

On Monday, the former Massachusetts governor gave voice to an idea that conservatives have been expressing - that a vote for Huckabee was a vote for McCain, on the theory that only Romney has any chance of stopping McCain.

Huckabee responded that it was "arrogant and presumptuous" for Romney to suggest he was the stronger candidate or would get the lion's share of Huckabee voters if the former Arkansas governor were not in the race.

After Huckabee won the convention in West Virginia, his campaign manager, Chip Saltsman, said: "Once again, conservatives have rejected Romney's convictionless campaign."

Romney's campaign manager, Beth Myers, noted that Romney had led on the first ballot in West Virginia only to lose on the second, alleging there had been a "backroom deal" between Huckabee and McCain that was meant to derail Romney.