Pennsylvania Republicans released their proposed Congressional map for the next decade today, and as expected mapmakers went to great lengths to shore up GOP Members in competitive districts.

The proposed map also moves Democratic Reps. Jason Altmire and Mark Critz into the same district, solidifying a matchup that has been anticipated for months.

Pennsylvania will lose one House seat in 2012 because the state’s population did not increase as quickly as others. Republicans control the state Legislature and the governor’s mansion, which means they control this cycle’s redistricting process.

Republicans suggested for months that they wanted to move Altmire and Critz into the same southwestern Pennsylvania district, and that’s exactly what they did.

The redrawn 12th district stretches from Beaver County on the western border, east through northern Allegheny County and all the way to Cambria and Somerset counties.

The construction of the 12th district signals that Altmire and Critz are in for a fair fight in the May primary. The district includes Altmire’s base in Beaver County and the northwest Pittsburgh suburbs, as well as Critz’s political base around Johnstown.

“Wow, it looks like they split it down the middle,” Jack Hanna, the chairman of the Pennsylvania Democratic Party’s southwestern caucus, said after looking at the map. “They’re going to make this thing lethally close as possible for each of them.”

But if Altmire wins the primary, he’d likely perform better in the general election. Altmire’s base includes a swath of Republican voters, whereas Critz’s base is mostly Democratic voters in Somerset and Cambria counties.

“I’m very happy,” Altmire said in a brief phone interview. “Of all the possibilities that were being discussed, this is really very favorable for me.”

Critz said in a statement, “I look forward to a spirited campaign.”

It’s no accident the 12th district also includes state Rep. Jim Christiana’s (R) base in Beaver County. Republicans have plotted for months to draw lines that paved the way for Christiana to run against the victor of the Altmire-vs.-Critz primary.

There were more surprises in the eastern part of the state, where Republican mapmakers aggressively redrew House boundaries to shore up GOP incumbents, in some cases shifting several counties and even cities into different districts.

The redrawn 7th district, a jagged U-shape, is particularly ugly and drawn to include parts of Berks, Lancaster, Chester, Delaware and Montgomery counties.

Republicans had two goals in mind with this meandering, barely contiguous district: to protect freshman Rep. Patrick Meehan (R) in competitive suburban Philadelphia and to ensure Rep. Joe Pitts’ (R) Chester County home remained in his Lancaster County-based 16th district.

Rep. Jim Gerlach’s (R) 6th district, a perennial target for House Democrats, moved north in Berks County and west into conservative Lebanon County. Mapmakers aimed to make his district less competitive in future cycles with these shifts.

But freshman Rep. Lou Barletta (R) was perhaps the biggest winner in the redraw — the partisan bend of his district changed more than any other member of the delegation. Mapmakers took what is currently a Democratic-leaning district and moved it west into Cumberland County in central Pennsylvania, keeping only his Hazleton base in Luzerne County.

Similarly, Rep. Tim Holden’s (D) district will flip from a heavily Republican district to become a safe Democratic seat under the new lines. Republicans moved the cities of Wilkes-Barre and Scranton into Holden’s district, which still includes his base in Schuylkill County.

Republicans also redrew districts held by GOP Reps. Charlie Dent and Tom Marino, adding more conservative counties in central Pennsylvania to make their districts safer. It’s doubtful Democrats could try to target either again under these new lines.

Under the new map, Democrats will probably view the seats held by GOP Reps. Mike Fitzpatrick and Mike Kelly as their most plausible pickup opportunities.

Republicans couldn’t do much for Fitzpatrick, whose Bucks County district in southeastern Pennsylvania borders New Jersey. Mapmakers also tried their best to shore up Kelly’s seat in northwestern Pennsylvania, but the GOP made sacrifices to ensure the redrawn 12th district remained competitive.

Some Pennsylvania GOP Members gave up significant amounts of Republican territory to shore up their more vulnerable colleagues in the redistricting effort.

Rep. Bill Shuster (R), who played a prominent role in the mapmaking, gave up more GOP territory than any of his colleagues. His loss in southwestern Pennsylvania made the redrawn 12th district more competitive.

To a lesser extent, Pitts, the dean of the delegation, acquired more competitive territory in Berks County in order to help Meehan and Gerlach.

Rep. Glenn Thompson (R) also picked up some Democratic territory in Erie County to make Kelly’s district safer for him.

Each district has a population of about 705,000, according to Pennsylvania lawmakers who unveiled the proposal at a committee hearing. The state Senate will vote on the map Wednesday morning, and the House will vote on the measure after that. Once the Legislature passes the new map, it will head to Gov. Tom Corbett’s desk for his signature.