By Louis Jacobson

PoliticsPA Contributing Writer

Pennsylvania will be losing a Congressional seat in 2012 – a long-expected fate made official in a Census Bureau announcement Dec. 21 – but it’s anybody’s guess who might lose out in the game of musical chairs.

Judging by interviews with a half-dozen political observers in the state, any number of the state’s 19 lawmakers could potentially be at risk — or gain — from a GOP-dominated remap. Here are some of the scenarios:

Rep. Mark Critz (D). Easily the most speculated-about redistricting casualty is Critz, whose southwestern Pennsylvania district was previously represented by the late, long-serving Democrat John Murtha. The district has leaned Republican in federal races in recent election cycles, and Critz, the least tenured Democrat in the delegation, won only narrowly in the 2010 general election, suggesting that modest changes in the district’s lines could be enough to push him out or send him into a head-to-head race in which he’d be the underdog.

In addition, Critz’ district sprawls like a flexing forearm over portions of nine countries, making it far from coherent – a legacy of the 2000 Republican-led redistricting effort that threw together Murtha with fellow Democratic Rep. Frank Mascara during an earlier round of Congressional delegation downsizing. So there’s little in its current configuration that would argue against some modifications.

On the other hand, any shifts of constituents designed to undermine Critz could weaken the GOP performance in the districts represented by Republicans Bill Shuster and/or Tim Murphy, and they may object to such a plan.

Reps. Mike Doyle (D) and Jason Altmire (D). Doyle’s district is believed to have lost population, but it can’t easily be discarded, because its strongly Democratic core of voters in and around Pittsburgh has to go somewhere. More to the point, Republicans would probably prefer to pack as many Democrats into Doyle’s district as possible, in order to remove them from GOP-held districts nearby.

However, to make up for its population losses, Doyle’s district might need to climb northward along the Ohio border, eating into the district represented by Altmire, who, like Critz, won a marginal district only narrowly in 2010. That, in turn, would force Altmire eastward, making him more vulnerable to a successful GOP challenge – an outcome Republicans would very much like to see.

Rep. Mike Kelly (R). In theory, Republicans would like to strengthen Kelly, a freshman who ousted a one-term Democrat from a fairly moderate district that stretches southward from Erie. But that would be tricky in practice.

The most Democratic portion of the district, Erie, would have to go somewhere, and unless the state map is radically redrawn, there’s only one district it could go to – the large, lightly populated district in north-central Pennsylvania represented by Rep. Glenn Thompson (R). Taking in a populous area like Erie would require some major changes to Thompson’s district lines, which he is unlikely to be happy about. Alternately, Erie could be split into two separate districts to dilute the Democratic strength, but that would divide a community of common interest and would likely raise hackles in that part of the state.

Rep. Tim Holden (D). Holden – who a decade ago defeated a more senior but less battle-hardened Republican incumbent, George Gekas, in a redistricting-prompted “fair fight” – is attracting increasing attention from GOP strategists involved in line-drawing. Holden, whose district heads northeast from Harrisburg, has won with relative ease, even in the GOP year of 2010, but his district leans Republican, so the GOP may attempt to do with line-drawing what the party has been unable to do at the ballot box.

Fortunately for the GOP, Holden’s district is surrounded by numerous Republican-held districts, allowing for several adjoining members to share the pain of losing Republican voters in order to make Holden more uncomfortable. These include GOP Reps. Todd Platts, Bill Shuster, Joe Pitts and Charlie Dent. Platts, Shuster and Pitts all have comfortable Republican seats, and while Dent’s district is more marginal, he’s won reelection consistently by adopting a moderate profile. In addition, several of these districts are thought to have gained population, meaning they’d have to shed constituents anyway. So for these Republicans, the impact of helping undermine Holden could be modest.

However, Republican candidates took over two other neighboring districts in 2010– the ones held by Lou Barletta and Tom Marino – and the GOP may make an effort to shore them up. If strengthening Barletta and Marino takes precedence over weakening Holden, then Holden can breathe easier. It’s also worth remembering that, as a post-redistricting fight survivor, Holden knows what it takes to win under the circumstances.

Rep. Jim Gerlach (R). Gerlach has consistently won reelection in his marginal-to-Democratic district, but most Republicans agree he could use some additional margin for error. One way would be to hand over a chunk of Montgomery County, such as Lower Merion, to Rep. Allyson Schwartz (D), who has an adjoining district. Despite occupying what was once considered a marginal district, Schwartz was reelected comfortably in 2010, suggesting that there’s little the GOP can do to oust her any time soon. So a giving Schwartz a new batch of Democrats currently in Gerlach’s district could be a wise move for the GOP.

Rep. Patrick Meehan (R). Meehan ended up winning his seat by double digits in 2010, but the Delaware County-based seat was previously held by Democrat Joe Sestak, and like much of southeastern Pennsylvania, it has trended towards the Democrats in recent years. So Republicans may try to add a Republican-leaning suburb or two from Pitts’ reliably conservative district, such as Kennett Square.