NASHUA, N.H. — Senator McCain rode the Straight Talk Express straight into first place in New Hampshire, and back into the thick of the race for the Republican presidential nomination.

“I hate to use to the word kid, but I think we showed the people of this country what a real comeback looks like,” the Arizona senator said in an interview today, savoring victory in the state he won eight years ago during his first White House bid.

“I’m grateful to the people of New Hampshire. I’m committed to keeping this country safe, and we’re going to move on to Michigan and South Carolina and win the nomination,” he added.

It was, indeed, a stunning comeback for the four-term senator who went from presumed front-runner a year ago to seemingly finished last summer after his campaign all but imploded. Mr. McCain not only stayed alive, but now heads into the next contest January 15 in Michigan with momentum and the potential to raise much-need money.

His triumph here sets up a high-stakes rematch with Mitt Romney in Michigan. Mr. McCain won there in 2000 and still has support there; Mr. Romney was reared in the state and is the son of a former governor. No other Republican plans to compete aggressively in Michigan, where economic issues will dominate and independents can vote in either party’s primary.

From there, Mr. McCain is angling for victory in South Carolina. He lags in polls in the military heavy state but hopes his Vietnam prisoner of war biography, decades of experience on defense issues, and staunch support of the Iraq war will outweigh Republicans’ deeply held anger about his position on immigration as well as their doubts about his loyalty to the GOP.

“Tonight’s results will show that we took a majority of all sections of the party, and we can do it again,” Mr. McCain said.

Since Labor Day and out of necessity, Mr. McCain spent most of his time and nearly all of his money — what little there was — in New Hampshire to right his struggling campaign. He sought to out-campaign his opponents with his freewheeling town-hall style events that encouraged back-and-forth dialogue with residents; he held 101.

Age 71, he traveled on his “Straight Talk Express” bus, a holdover from his first campaign, to all corners of the state arguing that he alone is best prepared to take on the threat of terrorism and restore trust in government, while countering Mr. Romney’s criticism that he was wrong on immigration and taxes. Mr. McCain earned the endorsement of more than two dozen New Hampshire newspapers, including the state’s largest, the New Hampshire Union Leader.

Outside events also broke in his favor.

The troop increase strategy he had long advocated helped curb violence in Iraq. After the comprehensive immigration bill he co-authored, which angered conservatives, died in Congress, Mr. McCain started telling voters he had gotten the message to “secure the borders first.”

At the same time, the nomination race grew even more fluid with no clear front-runner. Michael Huckabee rose and eventually defeated Mr. Romney in Iowa. In New Hampshire, Mayor Giuliani faded after dumping more than $2.5 million in TV, radio and direct mail into the state. A former Tennessee senator, Fred Thompson, was never a factor here.

Mr. McCain’s triumph capped a remarkable turnaround.

After losing to President Bush in 2000, he spent years preparing for his second chance and opened it with a flourish.

He mixed loyalists from his first candidacy with veterans of Mr. Bush’s two campaigns to build an unrivaled, and enormous, national organization. He cast himself as the inevitable nominee in a GOP that historically has nominated the next in line, and the only Republican who could unite a wayward party reeling from a 2006 thumping that put Democrats back in control of Congress.

But that appearance of invincibility quickly shattered.

Infighting rocked the campaign. Money was being spent faster than it came in, and finger-pointing ensued. Top aides vied for primacy making it appear that no one person was in charge and that Mr. McCain was not invested in the race. Longtime McCain aides clashed with one-time Bush aides.

Externally, Iraq and immigration took a political toll; his advocacy for a troop-increase strategy hurt him with independent voters while his backing for an eventual path to citizenship for millions of illegal immigrants infuriated the GOP’s conservative base.

His standing in polls dropped and fundraising dried up.

By summer, the campaign had blown through nearly all of the $25 million it had raised, and Mr. McCain had accepted the resignations of two top aides and promoted a third to manage what was left of the campaign; money troubles meant dozens of layoffs while loyalty to the departed aides prompted others to flee.

His candidacy in tatters, Mr. McCain laid low in August. He worked to stabilize his campaign’s finances and sought to map out a road ahead with a narrower strategy, hoping he could still emerge as the last man standing if the GOP field remained fractured.

New Hampshire was the obvious answer.

Eight years ago, the state made Mr. McCain. This year, Mr. McCain looked for it to save him — and save him it did.