Massachusetts Republican congressional candidate Richard Tisei, left, shakes hands with Joe McDonough in June. (Boston Globe/BOSTON GLOBE VIA GETTY IMAGES)

Richard Tisei is running a highly competitive campaign for Congress that could give Republicans their first House seat in Massachusetts in 16 years. And if Mitt Romney were going to have coattails, this is where they would be helping.

But the gay, pro-choice Tisei, a former state legislator who helped Romney secure some of his most important victories as governor of Massachusetts, is not exactly the typical face of the Republican Party. And with the former governor trailing President Obama by about 20 percentage points in Massachusetts, Tisei is keeping his distance.

“I consider myself a Goldwater conservative. My philosophy is, I’m a live-and-let-live Republican. My philosophy is, the government should get off your back, out of your wallet and away from the bedroom,” Tisei said earlier this month at a deli in this working-class hamlet near where he grew up.

It is another example of the trouble Romney has had building an effective political coalition which, for a former governor, would traditionally include kindred home-state legislators.

But Tisei, who served in the legislature for 26 years, is also seeking to make history as the first openly gay Republican to win a seat in Congress as a non-incumbent.

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The Republican platform opposes same-sex marriage and, if adopted into federal law, would prevent Tisei from marrying his longtime partner, Bernie Starr. Massachusetts law, however, allows for gay weddings and Tisei and Starr, who have run a real estate company together for many years, may be getting married after Election Day. “Stay tuned,” Tisei said of his marital plans.

Tisei’s candidacy has won the support of the entire House Republican leadership, including a $5,000 check from the PAC run by the vice-presidential nominee, Rep. Paul Ryan (R-Wis.).

And the prospect of picking off a seat in Massachusetts has galvanized conservative support from outside the state.

Polls show a close race against the incumbent Democrat, John F. Tierney. But Tierney is in dangerous territory politically, with about 40 percent support in most polls. Some of his troubles may be connected to the highly publicized indictments of his brothers-in-law for running a gambling ring. His wife pleaded guilty two years ago to “willful blindness” in overseeing the finances of the $1 million-a-year operation, which Rep. Tierney has said he believed was a legal online gaming business. One of the brothers-in-law is a fugitive in Antigua.

‘Fully behind him’

Republican leaders are actively helping Tisei’s campaign, and they promise that his sexual orientation and his liberal views on gay marriage and abortion rights would not make him an outcast in their conservative caucus.

“We all came here from somewhere. It is the opportunity that drew us here, and he will have every bit of opportunity, as an openly gay Republican, as any other Republican,” House Majority Leader Eric I. Cantor (R-Va.) said. “I told him, we’re fully behind him. I’m supportive of his candidacy and look forward to serving with him.”

For now, outside conservative groups are pouring more resources into the race than liberal groups. YG Action, founded by former Cantor aides, has spent more than $1 million on ads and mailings attacking Tierney on his ties to his brothers-in-law. The group now has a poll showing Tisei surging ahead of Tierney. Those ads are being followed up with two weeks’ worth of ads from the National Republican Congressional Committee, the group formally linked to GOP leadership. Among Democratic super PACs, the House Majority PAC last week canceled a $630,000 buy for advertising that would have gone against Tisei. The Democratic Congressional Campaign Committee has more than $1 million worth of advertising reserved in Boston, but it’s unclear how much of that will go toward helping Tierney or helping its candidates in two House races in New Hampshire.

The Tisei campaign has also become a rallying point for a cluster of wealthy Republican donors who support gay rights and would like to see the party move away from some of its recent harsh rhetoric on the issue.

Tisei has the financial backing of some of the most prominent gay conservatives, including Peter Thiel, the billionaire co-founder of PayPal, and Ken Mehlman, the former Republican National Committee chairman. Mehlman, now a private-equity executive, hosted a New York fundraiser for Tisei. A new super PAC supporting Republicans who approve of gay marriage — with financial backing from billionaire hedge fund manager Paul Singer — may enter the Tisei race in a few weeks.

Stealing a victory here would help buffer Republicans against Democratic efforts to take control of the House; Democrats need a net gain of 25 seats in November to secure the majority.

Tierney has attacked Tisei for his endorsements from Ryan and Cantor, saying he has sold out New England values for their financial backing. Democrats say a vote for Tisei is a vote for Ryan’s budget proposal that would eventually transform Medicare into a voucher system.

“Richard Tisei cannot get away from the most important vote he’s going to cast: John Boehner for speaker,” said Rep. Steve Israel (N.Y.), chairman of the Democratic Congressional Campaign Committee. “This is somebody who embraced tea party leaders.”

But Tisei’s long career, his views on abortion and gay marriage, and his sexual orientation have made it more difficult for Democrats to link him to the national GOP.

Many voters see Tisei as a local politician. “What you see is what you get,” said Bob Jancsy, 49, a plumber and registered Democrat who said he plans to vote for Obama and Tisei.

Wealth of credentials

Tisei’s first campaign for the state legislature began in 1984, while he was a senior at American University. Future U.S. senator Scott Brown, who grew up here in Wakefield, volunteered on the campaign. The two became allies and Tisei now refers to Brown, who is in a high-profile reelection race against Democrat Elizabeth Warren, as the “top of the ticket.”

After winning a state Senate seat in 1990, Tisei served in a near-powerless minority in heavily Democratic Massachusetts— at one point, the state Senate consisted of him, Brown, three other Republicans and 35 Democrats.

He was not in the closet, but he was not out of the closet. He often hosted lawmakers at dinners with his partner, Starr. When Romney fought a state Supreme Court ruling that legalized gay marriage, Tisei opposed his governor.

“I didn’t think I had to wake up and have a press conference and say: Hey, here I am,” he recalled. “I never told anybody I wasn’t gay. It wasn’t like I was hiding.”

In late 2009, as Tisei prepared to be his party’s lieutenant-governor candidate, he confirmed that he is gay in a Boston Globe interview. In 2010, Gov. Deval Patrick (D) was easily reelected and, for the first time since Tisei’s college days at American, he was out of politics.

Now trying to join Boehner — whose 2010 campaign manifesto included language opposing gay marriage — Tisei takes an evolutionary rather than revolutionary approach to gay rights and the congressional agenda. “If I’m in the caucus, people are going to see me, they’re going to get to know me. Just the fact that I’m there, is going to make a lot of people question, or think about the issue differently,” he said.

“Rather than poking somebody in the eye, the best way to deal with it is to let them evolve. I’ve seen all kinds of people, Democrats and Republicans, change their opinions of it over time,” he added.

This last point has driven Rep. Barney Frank (D-Mass.), the most-well-known gay member of Congress, and some other prominent gay advocates to vigorously campaign against Tisei, suggesting that his unwillingness to agitate will mean that he is a lesser advocate for gay rights.

“The fact that Richard Tisei is openly gay is a good thing. The problem is that it is of no use to us,” Frank said in a conference call organized by Tierney’s campaign.

Tierney, after warning seniors about Ryan’s Medicare plan at a retirement home in Peabody, Mass., said that Tisei “sold out and sold out early” to gain financial support from Boehner, Cantor and Ryan.

“He’s not an outspoken advocate,” Tierney said, saying his opponent ducks gay rights and other social issues.

Tisei rejects any attempt to link him with Romney, the tea party or national GOP leaders. “I’m, like, my own person. And at the end of the day, I do my own thing,” he said.