"You go to war with the army you have," said Christopher Borick, director of Muhlenberg College's Institute of Public Opinion.
With U.S. Rep. Jim Gerlach, former Gov. Tom Ridge and former U.S. Attorney Pat Meehan rejecting party leaders' requests to enter the Senate race, the GOP is coalescing around Toomey, who represented the Lehigh Valley in Congress from 1999 to 2005.
Toomey, 47, is often characterized - his supporters would say caricatured - as a right-wing ideologue, mainly due to his near-win campaign from the right against Specter in 2004. Specter hung on by less than 2 percentage points.
And, in a Democratic-trending state, the ultra-conservative label is an albatross in the general election, said John McNichol, chairman of the Upper Darby GOP.
It is increasingly difficult for a conservative Republican to get elected statewide in Pennsylvania, where Democrats now outnumber Republicans by 1.2 million voters.
"I think it weakens the general ticket," McNichol said of a Toomey Senate nomination.
However, Toomey was elected three times in a congressional district where Democrats hold the registration advantage. The 15th District, which includes Northampton County and most of Lehigh County, has also backed the Democratic presidential candidate in the last five elections.
"The pundits and all the sophisticated politicos were convinced I was going to lose," Toomey said of his 1998 campaign against Roy Afflerbach, a state senator and later Allentown's mayor. "I beat him - and it wasn't even close."
He won by 10 points.
Toomey's Senate campaign will likely focus on the economy and foreign policy, while avoiding divisive social issues. Or, as one local Republican strategist advised, "Look at what [defeated U.S. Sen.] Rick Santorum did, and do the opposite."
"I'm going to appeal to voters across the political spectrum with a message about ending the bailout and restoring economic prosperity," Toomey said.
Some Republicans are hoping for more bad economic news between now and Election Day. If the federal deficit continues to grow and President Obama's stimulus package doesn't perform as advertised, Toomey's message of smaller government and reduced spending could resonate next year, even in Pennsylvania, analysts say.
"The economic realities of 2010 will dictate a lot in terms of Toomey's ability to sell himself," Borick said.
"The people are absolutely going to be looking for change," said state GOP chairman Robert Gleason. "The stimulus is not creating any jobs."
Peg Luksik, the anti-abortion advocate and former gubernatorial candidate, also is seeking the Republican Senate nomination, but her campaign is not expected to gain much traction.
"I think that the Republican Party has united behind the candidacy of former Congressman Toomey," said Bob Asher, a member of the Republican National Committee from Montgomery County.
A Rasmussen Reports poll last month gave Specter, who was first elected to the Senate in 1980 as a Republican, a 50-39 lead over Toomey in the general election. Sestak, the Delaware County congressman who plans to challenge Specter in the Democratic primary, was leading Toomey 41-35.
However, those numbers don't necessarily mean much when the election is 16 months out.
"The perception that the race isn't close is wrong," said John Brabender, Santorum's former media consultant. "I think that Pat Toomey is starting to be seen as more of a consensus candidate." Toomey scoffs at the notion that he is unelectable.
"There's no substance to it," he said. "It is literally not possible to be elected to Congress in the 15th District otherwise."
Meanwhile, Republicans are reveling in the all-but-certain Specter-Sestak smackdown, which could leave the Democratic nominee deeply wounded next year.
"If [Toomey] can zero in on some issues outside of the social-conservative realm, specifically on fiscal and economic policy, where the Democrats will have liabilities, I think he can absolutely be competitive," said Borick, who has followed Toomey's political career. But whether he can compete in the voter-rich Southeast remains to be seen, said G. Terry Madonna, director of the Franklin & Marshall College Poll.
"Republicans cannot win if they can't hold their own down there," he said.