Mitt Romney officially stepped into the 2012 presidential race here Thursday by casting himself as the one Republican with the skills to heal the ailing U.S. economy and rein in Washington’s runaway spending.

The former Massachusetts governor, betting that a pitch focused tightly on the economy will resonate with a broad swath of voters, kicked off his second presidential campaign by trumpeting his record as a turnaround specialist in business and as head of the 2002 Winter Olympics. Romney also unleashed a broadside against President Obama, charging that he “has failed America.”

“Turning around a crisis takes experience and bold action,” Romney said. “For millions of Americans, the economy is in crisis today, and unless we change course, it will be a crisis for all of us tomorrow.”

In the wide-open battle for the GOP nomination, Romney is the nominal front-runner, but he has weaknesses that an array of potential rivals are aiming to exploit.

One of those, former Utah governor Jon Huntsman Jr., released statistics Thursday that purported to show a better record on job creation than Romney, as he prepared to set off on his own swing through New Hampshire. Another, former Alaska governor Sarah Palin, criticized Romney’s Massachusetts health-care plan ahead of her arrival in New Hampshire for an evening clambake.

Their criticism and campaigning is a fresh reminder to Romney that the nomination is anything but assured. Romney’s decidedly understated announcement speech on a windswept hayfield here was an indication that he aims to keep his campaign centered on the economy and on proving to Republican primary voters that he can go the distance.

Romney, 64, is trying to demonstrate he has learned the tough lessons from his failed 2008 bid. After being lampooned as too stiff, Romney sought to use Thursday’s kickoff to show he has become a more easy-going candidate.

In an open-collar shirt, his gelled hair flipping in the wind, Romney spoke on a farm trailer surrounded by bales of hay and lilac trees. The campaign kickoff was called “A Cookout with Mitt & Ann,” and indeed Romney and his wife dug into crockpots to dish out bowls of Ann’s favorite chili to supporters.

In his first go-round, Romney tried to be everything to everyone, jetting from early-voting state to early-voting state after his soaring announcement speech at the Henry Ford Museum in Dearborn, Mich. — a rollout he now says was “grandiose.” This time, with a far leaner campaign operation, Romney chose to declare his bid here in New Hampshire, a must-win state where he has deep roots and has focused most of his early campaign efforts.

“I am Mitt Romney, I believe in America, and I’m running for president of the United States,” he said, with a 250-year-old white barn and American flags behind him.

Romney’s no-nonsense 20-minute speech glossed over his vulnerabilities and signaled that he hopes to campaign on his own terms, taking his message past his Republican rivals and to the Democrats. He made the argument, as other candidates have, that he is electable — calculating, perhaps, that by tapping into Republican fears about four more years of an Obama presidency he can persuade primary voters to overlook his flaws.

Saying that “this country we love is in peril,” Romney blamed the nation’s unemployment and foreclosures on Obama, whom he accused of drawing “inspiration from the capitals of Europe.” Romney dismissed Obama as a novice who received the benefit of the doubt in 2008 by promising “to lead us to a better place.”

“Now, in the third year of his four-year term, we have more than slogans and promises to judge him by,” Romney said. “Barack Obama has failed America.”

Romney also promised to “return responsibility and authority to the states for dozens of government programs,” starting with “a complete repeal of ­Obamacare.” He referred to the health-care overhaul that is Obama’s signature domestic initiative — and that Obama’s advisers say was modeled in part on a measure Romney pushed through as governor of Massachusetts.

The Massachusetts law, which like Obama’s includes an individual mandate, is perhaps Romney’s biggest liability in the GOP primary. He made a single reference to it Thursday.

“I took it on and hammered out a solution that took a bad situation and made it better,” Romney said. “Not perfect, but it was a state solution for a state problem.”

Shortly before Romney spoke, Palin took aim at Romney’s law during a stop on her bus tour up the Eastern Seaboard.

“In my opinion, any mandate coming from government is not a good thing, so obviously . . . there will be more explanation coming from the former governor, Romney, on his support for government mandates,” Palin told reporters in Boston.

Palin arrived in New Hampshire later Thursday for an evening clambake in nearby Seabrook, marking her first visit to the Granite State since her 2008 run as the GOP vice presidential nominee.

Asked by reporters about Palin’s visit, Romney said: “It’s terrific. New Hampshire’s action central today.”

Romney drew a barrage of attacks Thursday from far beyond Palin’s shrink-wrapped bus. An aide to Huntsman distributed data to reporters showing that the unemployment rate was higher over a two-year period in Massachusetts than in Utah and Minnesota when Romney, Huntsman and presidential contender Tim Pawlenty were serving as governors in those respective states.

Democrats, meanwhile, tried to reintroduce the “flip-flopper” narrative that dogged Romney’s last campaign, releasing a video titled “Romney: Same Candidate, Different Positions,” that highlighted the candidate’s changing positions on health care and bailouts for the auto and banking industries.

In his 2008 race, Romney struggled to convince GOP primary voters that he was a trusted conservative despite having taken positions earlier in his political career — his support for abortion rights and same-sex marriage chief among them — that did not sit well with the Republican base.

This time, with the nation still slowly crawling back from a deep recession, Romney is banking on the economy trumping all else.

“From my first day in office, my number one job will be to see that America once again is number one in job creation,” Romney said.