STRATHAM, N.H. >> Mitt Romney’s political backyard is the most promising terrain in his second bid for the Republican presidential nomination. It’s also the most perilous.

The former governor from neighboring Massachusetts has a vacation place in New Hampshire, so the state really is his second home. He’s well known and well established here, and he’s putting more emphasis on the Granite State, which holds the nation’s first primary, than he did four years ago. He’ll be in Manchester for a seven-candidate debate Monday night.

But the state’s proximity to Massachusetts is a two-edged sword.

Voters know a lot about Romney’s health care program for Massachusetts, which included mandatory insurance coverage similar to President Barack Obama’s federal requirement that many conservatives detest. As a politician in liberal Massachusetts, Romney took stands now at odds with many GOP primary voters.

If his rivals can cripple or weaken Romney in New Hampshire, they might be able to overcome his impressive fundraising and experience in later-voting states such as South Carolina and Florida, their thinking goes.

“Romney is very strong in New Hampshire, and it’s his race to lose here and nationally,” said Jamie Burnett, a New Hampshire consultant who was Romney’s political director in the state four years ago. Burnett isn’t backing a presidential contender yet, a sign of the wariness that some former supporters feel about the candidate.

At the debate, it’s not hard to guess what line of attack the field will take on perceived front-runner.

Romney’s rivals on Monday night will be U.S. Rep. Michele Bachmann of Minnesota; businessman Herman Cain of Georgia; former U.S. House Speaker Newt Gingrich of Georgia; U.S. Rep. Ron Paul of Texas; former Minnesota Gov. Tim Pawlenty; and former U.S. Sen. Rick Santorum of Pennsylvania.

They will call Romney the intellectual godfather of the Democrats’ national health care law. They may note that in transitioning from a Senate candidate and governor of liberal Massachusetts to a pursuer of the GOP presidential nomination, Romney has changed his views on abortion and gay rights.

He has struggled to defend his record and cope with charges that he is inauthentic and opportunistic. His reversals on two contentious issues were true conversions of the heart, Romney says. He has defended his Massachusetts health agenda, somewhat awkwardly, by saying it was right for that state but it’s not a good model for the entire nation.

Romney is placing less emphasis this year on Iowa, which holds a caucus before New Hampshire’s primary. He announced his exploratory committee at the University of New Hampshire. He entered the race with an announcement in a farm field here last week. He helped bankroll the struggling state party. His advisers have kept in touch with past supporters, hosting regular get-togethers. Last week, Romney sent glossy — and costly — mailers to voters, hoping to reintroduce himself.

He has that vacation home on Lake Winnipesaukee, and many voters know him from his Massachusetts days, an advantage his rivals can’t match. The newspaper with the second largest readership in the state is The Boston Globe. The state’s population-heavy southern tier is in the Boston television market.

“Romney’s the guy to beat. He’s laid the groundwork,” said Kevin Smith, executive director of the conservative Cornerstone Policy Research. “But we’ll see if one of the other candidates can capture lightning in a bottle.”

Indeed, with high expectations come high risks. If Romney fares poorly in New Hampshire, it might be tough to recover in the South and West.

Pawlenty “has been running here for a year or more,” Burnett noted. If Romney stumbles and Pawlenty “is able to distinguish himself in the race, there’s a path,” Burnett said. The same might be true for former Utah Gov. Jon Huntsman, he said.

Pawlenty and others say Romney’s New Hampshire advantages easily can be overestimated.

“If the early polls were a good measure of who was going to win, Rudy Giuliani would be president or Howard Dean would be president or Hillary Clinton would be president,” Pawlenty dismissively told Fox News Channel in a newly aggressive tone that suggests he’s eager to go head to head with Romney as he tries to become the main alternative.

For now, Romney’s rivals are training their fire on his health care record, which was a model for Obama’s 2010 law. An AP-GfK poll in March found 82 percent of Republicans oppose Obama’s health overhaul.

Obama “said that he designed Obamacare after Romneycare and basically made it Obamneycare,” Pawlenty told “Fox News Sunday.”

“What I don’t understand is they both continue to defend it,” he said, previewing a line of attack in the debate. “I think it’s a dramatic overreach.

Huntsman, who is skipping Monday’s debate, said of Romney’s health care mandate: “In many minds, it isn’t anything about the costs associated with mandates. It’s the philosophy whether an individual has the right to make his own decisions.”

Former Alaska Gov. Sarah Palin may not run, but she too has criticized Romney for the health care law. “In my opinion, any mandate coming from government is not a good thing,” she said, and Romney must explain his position more convincingly.

Democrats are attacking too, possibly helping Pawlenty and the others.

Romney’s work in Massachusetts “helped lay the foundation” for last year’s health overhaul “and we will strongly defend both plans from attack,” said Eddie Vale, a spokesman for Democrats’ campaign to promote the law.

Democrats see Romney as the front-runner and the Democratic National Committee attacks him almost daily.

Romney has worked hard in New Hampshire, with mixed results. He had dinner this year with the publisher of The New Hampshire Union Leader, a newspaper that four years ago used regular Page One columns from publisher Joseph McQuaid to eviscerate Romney.

The private dinner with their spouses at the Bedford Village Inn was part of a charm campaign designed to put behind him a relentless campaign from the state’s largest newspaper that for decades has held outsized sway in GOP primaries.

It might not have made any difference. The day after Romney declared his candidacy at the farm, the paper’s front page was dominated by another political figure: Palin. A small box referenced a story about Romney’s announcement inside the paper.

And for all his behind-the-scenes efforts, voters aren’t seeing a lot of Romney at the traditional house parties and town halls. Romney has largely turned to columns and web videos to communicate with voters. He’s sought to limit his exposure, mainly because front-runners don’t struggle to earn attention.

“He’s the front-runner,” said Juliana Bergeron, the former chairwoman of the Cheshire County Republican Party. “He doesn’t need to introduce himself to voters like the others. Why put yourself out there?”

His lesser known rivals lack that luxury. For them, it’s their challenge to build up their name recognition — or tear down Romney’s here in his backyard.

Monday night will give them their first good chance.