SOUTHFIELD, Mich. — Mitt Romney, the former Massachusetts governor who scored his first major win in Michigan, said: “It’s a victory of optimism over Washington-style pessimism. The people of Michigan said they believe in someone who is going to fight for them.”

“I’m obviously very, very pleased,” the Republican presidential candidate said in a telephone interview tonight, moments after winning his native state.

“Now on to South Carolina, Nevada, Florida,” Mr. Romney said. “This campaign is going to go to all 50 states.”

He said he was pleased with his big advantage among Republican voters in Michigan, who far outnumbered independents and Democrats who could vote in either primary. Those voters preferred Senator McCain.

The victory was a needed elixir for a candidate who, while performing well, had faced questions about its national viability. Mr. Romney finished second to Michael Huckabee in the Iowa caucuses and Mr. McCain in the New Hampshire primary, despite heavy campaigning and $7 million of advertising in each state.

The doubts carried over to Friday, when anemic crowds greeted Mr. Romney upon his return to Michigan following a debate in South Carolina.

Yet over the weekend, an invigorated Mr. Romney stoked his home state’s concerns, pledging to pay better attention to Michigan’s ailing economy than any of his rivals, and chiding Mr. McCain after the Arizona senator said some of the auto industry’s lost jobs would never be recovered.

“I come from a good line of Romneys who care about people,” he said Saturday in Traverse City.

The former Massachusetts governor also played a sentimental card, traveling to Lansing to pose beneath his father’s portrait, dragging his first-grade teacher over to speak to reporters at a campaign stop and then touring the Detroit auto show, as he had 50 years before when George Romney ran American Motors.

In between, he told tales of summer vacations in the north country, of meeting his wife, Ann, at a high school party and he even paid tribute to Vernors, a local ginger ale. Tactically, Mr. Romney relocated more than a dozen senior staffers to Michigan to assist the local campaign staff.

“This is the day that’s going to change, I believe, the politics of our nation as we get ready to select our nominee,” Mr. Romney said today as he kicked off primary day with a rally in Grand Rapids, a Republican stronghold.

The air of confidence extended to Mr. Romney’s staff, which printed a Tuesday schedule including an 8 p.m. “victory” party in Southfield.

As he had since Iowa, Mr. Romney pointed to a dearth of private-sector experience for Mr. Huckabee, the former governor of Arkansas, and accused Mr. McCain of achieving few results despite nearly three decades in Washington.

“People have been talking about things that Washington has been promising for years but not delivered,” Mr. Romney said in Grand Rapids. “And so, I will go to Washington to stop the bickering, the sniping, the partisanship, the score-settling. I will go to Washington to actually get the job done for the people of America.”

Mr. Romney’s focus on Michigan was the first test of a strategic shift his campaign plans to follow for the remainder of the nominating contest.

While Mr. Romney initially envisioned a 50-state campaign launched by wins in Iowa and New Hampshire, the questions he got for second-place finishes in each contest, as well as the dearth of criticism Messrs. McCain, Huckabee, and Mayor Giuliani received for picking and choosing between the contests, prompted him to scale back and concentrate on a state-by-state effort.

Mr. Romney pulled back his television ads in South Carolina and Florida, reallocated the money to Michigan, and instead of the negative, comparative spots he used to pound Mr. Huckabee in Iowa and Mr. McCain in New Hampshire, he relied on a commercial showing him with his late father, who was governor from 1963 to 1969. Another featured a former collegue paying tribute to Mr. Romney’s help in the search for his lost daughter.

All told, the multi-millionaire spent more than $2 million on ads in the state, again the most of the Republican field.

Mr. Romney was headed to South Carolina tomorrow for a day-and-a-half of campaigning, before decamping to Nevada. Both states vote January 19, and while Mr. Romney has trailed in South Carolina polling, he has been the only Republican candidate to pay attention to Nevada. Those facts prompted his staff to focus where it had the greatest potential for victory.

Going forward, Mr. Romney is targeting Florida, which votes January 29, as well as the numerous states voting on February 5, when 1,038 delegates will be awarded in caucuses and primaries from coast to coast. Mr. Giuliani has essentially skipped all the early contests to focus on Florida and the February 5 states.