Pennsylvania, the center of the political universe this week, will again garner outsized attention in this fall’s midterm elections.

Though Tuesday’s House primaries were greatly overshadowed by the nationally significant victories of Rep. Joe Sestak in the Democratic Senate primary and of Mark Critz (D) in the 12th district special election, they did set up some key November matchups in the quintessentially competitive Keystone State.

Roll Call’s current House race ratings include 10 of Pennsylvania’s 19 districts as among the 104 districts that will hold competitive elections this fall — the most in any state.

“Pennsylvania will be the ultimate bellwether this year, because we have more competitive Congressional seats than any other state in the union,” said Charlie Gerow, a Pennsylvania-based Republican strategist. “Pennsylvania is, it’s fair to say in the red-blue continuum, a very purple state right now.”

The 10 districts at stake include eight Democratic-held districts where the odds of a Republican takeover range from serious to long shot. A strong showing in Pennsylvania is vital to Republicans’ efforts to make the net gain of 40 seats needed to capture the majority.

“Pennsylvania will play a key role this fall because there are several GOP pickup opportunities stretching from Erie to the Philadelphia suburbs,” said Tory Mazzola, a spokesman for the National Republican Congressional Committee.

The GOP effort to build momentum ahead of November suffered a setback Tuesday, when Critz defeated businessman Tim Burns (R) by an unexpectedly large 8-point margin in the race to succeed the late Rep. John Murtha (D).

Shripal Shah, a spokesman for the Democratic Congressional Campaign Committee, suggested that Critz’s victory augurs well for Democrats outside the 12th district.

“Pennsylvanians rejected the Republican candidates [Tuesday] because they ignored local interests and issues, and other Republicans should expect similar results in six months,” he said.

Critz will run with the institutional advantages of incumbency in a November rematch with Burns. GOP officials said the voter turnout model in November will be more favorable and that Critz, who was a first-time candidate for office, will now amass a voting record they think they can exploit.

Another Pennsylvania rematch will take place in the Scranton-area 11th district, where 13-term Rep. Paul Kanjorski (D) will face Hazleton Mayor Lou Barletta (R) for the third time in eight years. The Congressman won their most recent race, in 2008, by just over 3 points.

Kanjorski’s weakness in the Democratic primary — he won just 49 percent of the vote against two challengers — suggests he will have trouble holding the Democratic base in a district that usually votes strongly for that party. Kanjorski will tout his seniority as helpful to Pennsylvania.

The best GOP takeover opportunity in Pennsylvania is in the only open-seat race, in the suburban Philadelphia 7th district that Sestak is relinquishing to run for Senate.

Neither Pat Meehan (R), a former federal and county prosecutor, nor state Rep. Bryan Lentz (D) faced primary opposition, a testament to the high regard with which party officials hold their candidacies. Meehan is better-funded than Lentz but will need to exhibit crossover political appeal to win a district that has been drifting Democratic.

Republicans face longer odds in dislodging a pair of junior Democratic incumbents from culturally conservative districts in the west.

In the Erie-based 3rd, Republicans have indicated that they will make Rep. Kathy Dahlkemper’s vote for the health care bill a defining issue. Their candidate is Mike Kelly, a businessman who will need to forge party unity after winning a bruising six-candidate primary with 28 percent of the vote.

In the 4th district, which takes in some suburbs of Pittsburgh, Rep. Jason Altmire (D) will face Keith Rothfus (R), a businessman with tea party ties who trounced Mary Beth Buchanan, a former federal prosecutor who had been recruited by the NRCC and was seen as the candidate of the GOP establishment.

Jon Delano, a western Pennsylvania-based political analyst, said that he was surprised by the 2-1 ratio by which Rothfus won the primary and that the outcome “suggests that, particularly in the Republican Party, there’s a very strong tea party movement at work.”

“That’s going to be a fascinating election to watch,” Delano said of the Altmire-Rothfus matchup.

Like the 4th, Republicans also are targeting the northeastern 10th district because it voted comfortably Republican for president in 2008. Tom Marino, a former prosecutor at the county and federal levels, won a three-candidate primary and will face two-term Rep. Christopher Carney (D).

In yet another rematch, Rep. Patrick Murphy (D) will square off against former Rep. Mike Fitzpatrick, who lost their first head-to-head race four years ago in the suburban Philadelphia-based 8th district.

In a sign that Murphy is taking the race seriously, he’s already challenged Fitzpatrick to at least eight debates and attacked him on environmental and trade policy.

Of the eight Democratic-held districts that Republicans are eyeing, their longest shot is in the east-central 17th, where nine-term Rep. Tim Holden will go against state Sen. Dave Argall.

Holden’s vote against the health care bill was a liability in a Democratic primary he won with 65 percent of the vote, but it will be an asset in the general election for a Congressman who has long projected an image as a Democratic centrist. And Argall has a lot to prove as a general election candidate after winning a four-candidate GOP primary with just 32 percent of the vote.

Democrats will mostly contest Pennsylvania districts from a defensive position. They see opportunities for gains in the 6th district, a swath of suburban and exurban Philadelphia that four-term Rep. Jim Gerlach (R) is defending, and in the Lehigh Valley-based 15th district, where Rep. Charlie Dent (R) is seeking a fourth term.

Those two districts are among just six nationwide that voted Democratic in both the 2004 and 2008 presidential races but are represented in the House by a Republican.

“We’ve said from the start of this cycle that the best defense is a good offense,” Shah said.

In the 6th, physician Manan Trivedi (D) will face Rep. Jim Gerlach (R) after narrowly defeating Doug Pike, a wealthy former newspaper editorial writer. Democrats like Trivedi’s image as a nonpolitician and a surgeon who served during the Iraq War, although he will need to intensify his fundraising to run strongly against Gerlach, who has always run well-funded, and very close, campaigns.

“We think it’s going to be a very spirited race,” Gerlach said.

Money is less of a concern for Democrats in the 15th, where Bethlehem Mayor John Callahan is among the best-funded challengers in the nation. He’ll have to puncture Dent’s long-cultivated image as a popular Republican centrist.