As House Republicans look to put more Democrats on defense in 2010, they will undoubtedly take notice of the fertile playing field in Pennsylvania’s 4th district.

Voters in the district north of Pittsburgh have picked Republican presidential candidates by increasing margins since 2000. Sen. John McCain (R-Ariz.) received 55 percent of the vote there last cycle — 1 percent better than President George W. Bush’s total in 2004.

But while the presidential numbers seem favorable for the GOP, Rep. Jason Altmire flipped the district into the Democratic column in 2006 and then defeated former Rep. Melissa Hart (R) again in a 2008 rematch by an even larger margin.

Now that Hart has declined to run again this cycle, Republicans are searching for a suitable challenger to Altmire — and they might have found their man.

The National Republican Congressional Committee has had several conversations with state House Republican Whip Mike Turzai about running against Altmire. Turzai, who did not respond to an interview request for this story, also attended the NRCC’s annual dinner in March.

Other often-mentioned Republicans, including former Pittsburgh Steelers star Lynn Swann — who got a drubbing in the 2006 gubernatorial race — and state Sen. Jane Orie, are not interested in running.

Altmire, meanwhile, remained bullish about his re-election prospects in an interview last week. While he called McCain a “perfect fit— for his district, he pointed out that 2010 is not a presidential cycle.

“McCain demographically was a very credible candidate,— Altmire said.

He also said he’s aware that Turzai, whom he called a friend, is looking at running against him.

“I know that he’s being recruited,— Altmire said. “I haven’t heard that he’s considering it. He ran for this seat in 1998. It did not work out very well.—

By most accounts, Turzai’s 1998 bid for the seat against then-Rep. Ron Klink (D) was a less-than-stellar campaign. He lost to Klink, 36 percent to 64 percent, in a district that two years later gave 50 percent of the vote to Bush.

During that first campaign for the 4th district seat, Turzai was derailed by two major publicity mishaps. Two of his supporters got into an altercation with Klink on the sidewalks of Pittsburgh while trying to videotape him for a negative campaign advertisement. Klink also blasted Turzai for sending a helicopter to take aerial footage of his home as an invasion of his privacy.

Klink left the seat in 2000 to unsuccessfully challenge Sen. Rick Santorum (R), who also represented a large part of the 4th district when he was in the House. Hart represented the district for four terms until Altmire defeated her in an upset in 2006.

Turzai was elected to the Pennsylvania House in 2001, where he rose quickly to be the second-ranking Republican in Harrisburg. But Turzai’s ties to the state capital could be a double-edged sword for the Republican. While he has earned his stripes as an elected official, Democratic strategist J.J. Balaban said it’s hard for any candidates to shake recent scandals in the state legislature.

“It’s hard to believe that he hasn’t indulged in any of the sins of Harrisburg,— Balaban said. “That’s for pretty much any member of the state House, in pretty much any party.—

Balaban, who has worked for Klink and other Democrats in the 4th district, cautioned that Altmire is no Rep. Robert Brady (D) — the Philadelphia party boss who has not won with less than 80 percent of the vote in the last 10 years — but his anti-abortion views make him a viable Democrat in the suburban Pittsburgh district.

“The trend in western Pennsylvania is that it’s generally becoming more conservative, but it’s still pretty good ground for a pro-life Democrat,— Balaban said.

In fact, Altmire is in good company. All Democratic Members outside the Philadelphia area consider themselves to be anti-abortion: Altmire and Reps. John Murtha, Mike Doyle, Kathy Dahlkemper, Christopher Carney and Tim Holden.

The right Republican candidate, according to Pennsylvania GOP strategist Ray Zaborney, will be a Republican who has similar socially conservative views — and he said Turzai fits the bill.

“The district is getting more conservative, and I think it’s a district that Republicans are going to get back … either this cycle or sometime in the coming years,— Zaborney said.