Republican Party leaders, who only a few weeks ago viewed the GOP presidential nomination race as wide open, now consider it a two-man contest between Rick Perry and Mitt Romney, and they are choosing sides in what many think could be a long and potentially divisive campaign.

In interviews this week, more than a dozen governors, law­makers, major donors and strategists said they are studying recent debates and polls to determine whether Perry, the governor of Texas, or Romney, a former governor of Massachusetts, would present the strongest challenge to President Obama. They signaled that endorsements and other measures of support could flow in coming weeks as Perry and Romney press their cases privately to potential backers.

“They wouldn’t say it publicly, and I won’t name names, but as a general consensus, most of us in the cloakroom and around our caucus meetings believe it’s down to a two-man race,” said Sen. James M. Inhofe (Okla.), who has endorsed Perry. “More and more Republicans are looking at electability.”

The nominee will define the Republican Party for the 2012 campaign cycle, making the choice consequential for the GOP’s hopes of taking back the Senate and maintaining control of the House. That has top Republicans nationwide especially tuned in to potentially damaging rhetoric, such as Perry’s comments about Social Security, which he labeled a failure and a “Ponzi scheme.”

On Capitol Hill, the chiefs of staff to Florida’s GOP members echoed those concerns in a private meeting Monday, according to a Republican source with knowledge of the meeting who spoke on the condition of anonymity. The person said Perry’s Social Security comments effectively “chilled” an expected wave of endorsements from conservative members of Congress.

Bringing in endorsements

Although Louisiana Gov. Bobby Jindal, a rising star in the party, endorsed Perry on Monday, and Nevada Gov. Brian Sandoval, who was elected last year, endorsed him on Tuesday, others said many Republicans will want to see how Perry handles himself over the next few weeks.

“It’s the wait-and-see-how-he-does wave,” said Tom Perdue, a Republican strategist in Georgia. “If he can make it through 60 days without the media just tearing him up, then I think he’s going to get another wave of support.”

Many Republican leaders said they will choose the candidate who is most electable — the one who can best balance the conservative ire that has fueled the tea party movement and the pragmatism that is required to navigate what party leaders are certain will be a treacherous general election.

Worries about Perry’s electability in part pushed former Minnesota governor Tim Paw­lenty to endorse Romney this week. Perry and other candidates had courted Pawlenty after he dropped out of the race following August’s Iowa Straw Poll. But Pawlenty decided to back Romney after he and his wife, Mary, spent a quiet weekend with Romney and his wife, Ann, at their vacation home on New Hampshire’s Lake Winnipesaukee.

In phone calls and get-togethers, Perry, Romney and their surrogates are pushing influential Republicans to abandon what has been their wait-and-see approach. During a dove hunt last weekend in Altus, Okla., for instance, Inhofe said he asked Sen. John Cornyn (R-Tex.) to get behind his home-state governor. Cornyn responded that he wouldn’t choose sides because he chairs the National Republican Senatorial Committee, Inhofe said.

In private, Perry and Romney have been making largely the same appeals they’ve been making in public. At a closed-door meeting with donors in Los Angeles last week, Perry boasted of his undefeated record in 10 straight Texas elections, according to a donor who was present. The governor did not criticize his Republican opponents and tried to shed the perception of him as an ideologue by pointing out that he has praised Obama for the killing of Osama bin Laden.

Romney’s pitch, meanwhile, centers on the skill set he developed in the business world, which he says prepares him to turn around the economy. He increasingly is making an electability argument, saying he would be the party’s strongest candidate in general-election battlegrounds.

“I’m not bashful about saying, ‘Here’s why I support Mitt, and I think he’ll be a great leader for our whole country,’ ” said Nebraska Gov. Dave Heineman. “The question is: What’s going to happen in Pennsylvania, Ohio, Michigan, Wisconsin, Nevada, New Mexico? Those are states that we need to win, and that’s where I think Governor Romney has a better shot.”

Rep. Jason Chaffetz (Utah), another Romney backer, is working Capitol Hill to attract other tea-party-aligned lawmakers to Romney’s side.

“What I tell my colleagues is: ‘Governor Romney is the most well-vetted candidate out there. We know where all his warts are and it doesn’t look that bad. In fact, it looks pretty good.’ ”

Part of both men’s strategy is to shore up perceived weaknesses. Perry already appeals to tea party activists and is seeking to build support from within the GOP establishment, whereas Romney enjoys an establishment imprimatur and is courting freshman House members and others who give him juice with grass-roots conservatives.

Rep. Mo Brooks (Ala.), a tea- party-backed freshman, said that neither Perry nor Romney has called him. But their surrogates have sent “indirect feelers.” This is the message Brooks said he sent back to the campaigns:

“I will probably be voting for the Republican who I believe is going to beat Barack Obama by the most. The one that’s going to beat Barack Obama by the largest percentage is the one that will best help us capture the Senate and improve our margin in the House.”

Untapped support

Among officeholders, there remains a huge reservoir of untapped support. So far Romney has won the backing of two governors, two senators and 11 House members. Perry has two governors, one senator and eight House members.

The Perry and Romney campaigns are urging donors to get on board before Sept. 30, when the third fundraising quarter ends.

Perry’s fundraising “bundlers” are making a decidedly non-ideological pitch. They argue that since Romney has spent years building a tight-knit fundraising network, new donors won’t have much access to him, while entry to Perry’s inner circle is easier at this stage.

At the same time, the race has taken on a negative tone, stoking fears among party leaders that a long primary battle could weaken the eventual nominee and give Obama a head start.

“President Obama is going to raise nearly a billion dollars,” Chaffetz said. “We don’t have the luxury of waiting another six months to figure out who’s going to be our nominee.”

For all the talk of a Perry-Romney duel, however, some Republicans cautioned that the contest could change once again.

In Iowa, home to the nation’s first caucuses, Rep. Michele Bachmann (Minn.) is positioned to do well and perhaps win. And in New Hampshire, Republicans said Jon Huntsman Jr., a former Utah governor, should not be counted out.

“It is a two-man race, but it might not be next week,” said Ed Rogers, a longtime Republican operative. “It could change based on whether somebody slips on a banana peel.”