Call it a summer slump, but since our last congressional-seat vulnerability ranking in April, the broad outlines haven’t changed much. However, a few contests have risen or fallen slightly

The two most vulnerable seats remain the one held by Democratic Rep. Mark Critz in western Pennsylvania and the one held by Republican Rep. Mike Fitzpatrick in the Philadelphia suburbs. Next on the list, a notch less vulnerable than either Critz or Fitzpatrick, are GOP Reps. Jim Gerlach and Tim Murphy.

The GOP can celebrate two districts where their candidate looks somewhat safer than they did three months ago – the seats held by Reps. Pat Meehan and Charlie Dent.

As always, these ratings are based on consultations with a range of state and national political experts. We list the seats in descending order of vulnerability, which we define as the likelihood of the seat switching party control in the 2012 election. We’ll be publishing new rankings periodically throughout the rest of the campaign season.

Here we go:

Vulnerable

1. Mark Critz (D, 12th district)

Both sides agree that the matchup between Critz and his Republican challenger Keith Rothfus remains the marquee congressional race in the Keystone State this year, and it will likely stay atop our list to the end. Both candidates have their work cut out for them – starting with simply getting known to voters in the sprawling, redistricted western Pennsylvania district. Rothfus benefits from the general Republican leanings of the district – hammered Critz for voting against a House Republican effort to repeal President Barack Obama’s health care law, the first of what will be many efforts to drive a wedge between Critz’s loyalty to his party and to the district’s ideological leanings. (For instance, Rothfus hit Critz on hosting a fundraiser for Rep. Allyson Schwartz, D-Pa., who is a prominent abortion-rights advocate.) Still, Critz’ on-the-ground experience – honed during years as an aide to the late Democratic Rep. John Murtha – combined with his strong backing from labor unions roughly evens the playing field. Both sides have something to crow about from the second quarter fundraising figures: Critz raised more in the quarter, ($596,496, compared to $400,000 for Rothfus), but Rothfus had $650,000 cash on hand, compared to $428,000 for Critz, who saw some of his warchest drained by a tough intra-party primary against Rep. Jason Altmire. A Democratic poll in early July had Critz up, but only modestly — 44 percent to 38 percent. Barring something unexpected, this race will go down to the wire.

(Previous ranking: No change)

2. Mike Fitzpatrick (R, 8th district)

The main reason Fitzpatrick is vulnerable is that he’s running in a swath of moderate, Philadelphia-area suburbs with lots of Obama voters. This means Fitzpatrick will have to secure a lot of ticket-splitting voters to win, a challenging task in this polarized environment. On the other hand, Fitzpatrick has a proven record of winning votes in the district’s heart, Bucks County. Democrat Kathy Boockvar has put together a credible fundraising effort. She took in $330,000 in the second quarter – less, but not dramatically so, than the incumbent, who collected $395,000. Fitzpatrick still has a cash-on-hand lead of $1.2 million to $421,000. The GOP is still attempting to paint Boockvar as a “radical activist” whose former employer did work for ACORN and is run by “left-wing bomb throwers like Harry Belafonte.” Whether this line of attack works in this type of district remains to be seen.

(Previous ranking: No change)

Potentially vulnerable

3. Jim Gerlach (R, 6th district)

Gerlach got a bit of a cushion when his seat was redistricted, but the race remains competitive, thanks to solid fundraising by Democratic physician and 2010 challenger Manan Trivedi. Trivedi, a onetime battlefield surgeon, raised $260,000 in the second quarter. That’s less than Gerlach with $341,000, and Trivedi’s cash on hand ($527,000) trails Gerlach’s ($885,000). Still, Trivedi’s cash-on-hand figure is higher than any other Democratic challenger in the state, and he has experience from his 2010 run.

(Previous ranking: tie for 4th, potentially vulnerable)

4. Tim Murphy (R, 18th district)

Murphy has been potentially vulnerable in the past, but this year he finally has a serious challenger: Larry Maggi, a former Marine, state trooper, sheriff and county commissioner. Murphy has $1 million-plus cash on hand, but Maggi has a respectable $408,000 after raising $230,000 in the second quarter. More strikingly, Maggi has reserved $495,000 in television ad time in Pittsburgh for the fall – more than five times the largest previous ad buy by a Murphy challenger.

(Previous ranking: 3rd, potentially vulnerable)

5. Pat Meehan (R, 7th district)

On the one hand, this district – which zig-zags through Montgomery, Delaware, Chester, Lancaster and Berks counties – should be pretty fertile territory for a Democratic candidate, since it lies in one of Obama’s strongest parts of the state. But Democratic challenger George Badey, an attorney, hasn’t fared as well in the fundraising game as fellow challengers Boockvar, Trivedi or Maggi. That puts a big crimp in his prospects, particularly given the expensive media market he’s running in. Badey raised only  $104,000 in the quarter and has $205,000 on hand – far below the $498,000 Meehan raised in the quarter and the $1.4 million the incumbent has on hand. Throw in the fact that Meehan doesn’t appear to have said anything too offensive and you have a contest that seems poised to slip down our vulnerability list.

(Previous ranking: tie for 4th, potentially vulnerable)

Minimally Vulnerable

6. Lou Barletta (R, 11th district)

Barletta is a heavy favorite, thanks to a strongly Republican district and $335,910 cash on hand. But Democratic challenger Gene Stilp – a surprise winner in the primary – has an off chance of becoming a breakout candidate. Stilp, best known for his pink, pig-shaped bus, nearly knocked off a Republican incumbent for a state House seat in 2010. Barletta, while well known for his stance against illegal immigration as Hazelton mayor, is a newcomer to much of the district, and this is the kind of inexpensive media market where a modest investment can have an impact. Even so, Stilp’s fundraising record so far has been anemic — $12,079 raised and $14,313 cash on hand.

(Previous ranking: 8th, minimally vulnerable)

7. Mike Kelly (R, 3rd district)

Kelly remains one of the most outspoken members of the Pennsylvania delegation – a trait that resurfaced recently when he compared abortion- related provisions of Obama’s health care law to the terrorist attacks of Sept. 11, 2001. Meanwhile, Kelly’s Democratic opponent, professor and primary winner Missa Eaton, notched a bit of a victory when she beat out a number of better-known candidates to win a challenge sponsored by the Pennsylvania Democratic Party to amass the most online votes of any Democratic challenger in the state. A spiral of grassroots support combined with verbal stumbles by Kelly could vault this race into higher gear, but for now, Kelly has a comfortable lead in money. Kelly beat Eaton in second-quarter fundraising, $164,000 to $83,000, and leads her in cash on hand, $389,000 to $21,000.

(Previous ranking: 7th, minimally vulnerable)

8. Tom Marino (R, 10th district)

Though he faces a big challenge in unseating Marino, a former U.S. Attorney, in this strongly Republican district, Democratic businessman Phil Scollo is drawing at least a little positive attention. He released an internal poll that showed Marino under the crucial 50 percent line for an incumbent. That said, Marino still led in the poll, 47 percent-30 percent – and, as always, leaked internal polls should be taken with a strong dose of salt. Marino still has a strong lead in the money game — $300,000 to $36,000 in cash on hand.

(Previous ranking: 9th, minimally vulnerable)

9. Charlie Dent (R, 15th district)

Dent, one of his party’s dwindling number of moderates, has been a survivor in his swing Lehigh Valley district, and the Democrats’ failure to gain traction is particularly noticeable this year. His challenger, Lehigh County Democratic Chairman Rick Daugherty, had a minuscule $3,121 on hand at the end of the quarter.

(Previous ranking: 6th, potentially vulnerable)

Not vulnerable

10 (tie). Joseph Pitts (R, 16th district)

As we’ve noted before, Aryanna Strader has an interesting profile – she’s a veteran and a businesswoman – and the district is not as solidly Republican as some others in the state. But Strader raised just $10,000 in the second quarter, demonstrating that she’s no threat to long-serving incumbent Pitts. Whenever Pitts retires, either Strader or some other Democrat will probably make a more plausible run at this seat.

(Previous ranking: 10th, minimally vulnerable)

10 (tie). Open seat (Tim Holden, D, defeated in primary, 17th district). (Previous ranking: 11th, not vulnerable)

13 (tie). Open seat. (Todd Platts, R, retiring, 4th district). (Previous ranking: 12th, not vulnerable)

13 (tie). Bob Brady (D, 1st district.) (Previous ranking: No change).

13 (tie). Chaka Fattah (D, 2nd district) (Previous ranking: No change).

13 (tie). Glenn Thompson (R, 5th district). (Previous ranking: No change).

13 (tie). Bill Shuster (R, 9th district). (Previous ranking: No change).

13 (tie). Allyson Schwartz (D, 13th district). (Previous ranking: No change).

13 (tie). Mike Doyle (D, 14th district). (Previous ranking: No change).