Congressional redistricting is a game of musical chairs that starts once a decade, when the census updates population figures. This year, both Pennsylvania and New Jersey grew more slowly than other states, so each is losing a seat in the House of Representatives.

Pennsylvania, like most states, lets its legislature draw the new map. On Tuesday, the state House released a map that combines two southwestern districts, which could pit two incumbent Democrats against each other next year. It also redrew some competitive districts to protect Republican incumbents. Democrats were particularly peeved at the remapping of a Philadelphia-area district, the Seventh, which would take in parts of five counties. They likened its shape to an oil spill.

The results in New Jersey, on the other hand, are still up in the air. The state is one of seven that uses a committee to redraw its map. The committee - six Democrats, six Republicans, and an independent tiebreaker - will hole up in a New Brunswick hotel for three days next week in the hope of agreeing upon a map by Wednesday.

"It's a noble goal," John Farmer Jr., the tiebreaker and the dean of Rutgers School of Law in Newark, said with a laugh Tuesday. "We'll see how it plays out."

New Jersey has until Jan. 17 to complete that map, but Farmer, a former state attorney general, said he hoped to have it done sooner.

In Pennsylvania, where the GOP controls the legislature, most observers figured a Democratic district would be targeted for elimination. Sure enough, the map released this week combines Democratic parts of the southwest's 12th District, represented by freshman Mark Critz, with the district of fellow Democrat Jason Altmire. GOP-prone parts of Critz's turf were allotted to neighboring Republican districts.

But in New Jersey, speculation continues to swirl about which of the 13 districts will be axed, putting incumbents on tenterhooks.

"There are so many potential scenarios here that it's difficult to lay odds on which one is the most likely," said Patrick Murray, a political analyst and director of the Monmouth University Polling Institute. "There are a few folks who we know are safe because of the Voting Rights Act or because of geography."

The U.S. Voting Rights Act prevents map revisions that shatter a minority population's majority within a district. In New Jersey, that means the African American majority in the 10th District, centered in Newark, and the Hispanic majority in the 13th, which includes most of Hudson County, must be preserved.

And since each district must add some voters, the fastest growing areas of the state - in South Jersey - will add the fewest and therefore could escape major changes. Republican freshman Jon Runyan, whose lack of seniority could otherwise make him a target in redistricting, may be protected by population growth in his district, which includes parts of Burlington, Ocean, and Camden Counties, Murray said.

But like other southern districts, Runyan's will likely be stretched north to pick up voters, which could make his district more competitive, Murray said.

Another scenario would push Democratic incumbent Rush Holt into the same district as Republican Leonard Lance in the central part of the state. "Lance-Holt, it probably makes the most sense because of the way the districts are currently drawn," Murray said.

Other rumors pit GOP incumbent Rodney Frelinghuysen against either Garrett or Lance, or an all-Democrat fight between Holt and U.S. Rep. Frank Pallone. But Murray and others think Farmer will be more inclined to split New Jersey evenly - six Democratic districts, six  Republican - rather than tilt the map to favor either party.

Farmer brushes off the speculation. He'll get his first glimpse of the proposed maps Monday. More than anything, he said this week, it's about the demographics.

"I don't have any preconceptions going into this," he said. As for whether he considers New Jersey a Democratic state - as was argued by Alan Rosenthal, the tie-breaking member of the legislative redistricting committee - Farmer said, "New Jersey is really an independent state more than anything else."

Meanwhile in Pennsylvania, the state Senate was to vote Wednesday night on the map that Republicans had drawn and liked. Democrats talked of going to court - as the losing party often does after the maps are drawn.

Neutral observers assumed Republicans would redraw lines to tighten their grip on 12 of the state's 19 districts. But "they pushed it about as far as it can possibly go, legally," said Chris Borick, a political scientist at Muhlenberg College. He said the new lines fall just short of "tortured."

Borick said, "The very design of these districts really does, of course, express undeniable partisan goals."

 
Contact staff writer Joelle Farrell at jfarrell@phillynews.com, 856-779-3237 or @joellefarrell on Twitter.