But the oscillating electorate soon reversed that advantage, and then reversed it again. After the 2006 elections that gave Democrats control of the House, Democrats held 11 of the state's 19 seats in the chamber. But they will give their in-state majority back when the new Congress takes office next month, and Republicans again hold 12 of Pennsylvania's House seats.
The lesson from Pennsylvania, for both parties, is to pad safe districts, funneling voters from the opposition party into as few districts as possible, rather than go for the maximum number of winnable seats. The temptation to grow overly aggressive can be even greater in swing states, where the parties try to gain more congressional seats instead of opting to consolidate and defend. That creates districts where the electorates are closely divided and lawmakers are vulnerable to every shift in the voting trends--a situation that has been especially pronounced in the last three election cycles, when Democrats picked up 55 seats in two consecutive elections only to see all of their gains (and then some) wiped out in November.
Experts say that the GOP should keep those lessons in mind as it flexes its freshly won muscle.
"It's an embarrassment of riches for the Republicans," said Michael McDonald, a political scientist at George Mason University who studies redistricting. "Usually what you'd want to do with the redistricting plan is expand the map; but I think the Republicans are going to be in a position to just protect what they've gained in 2010 rather than to expand. The Republicans have pretty much maxed out the number of seats that they can win. If anything, they've won too many seats, because many of these Republicans have won in Democratic-leaning seats and they're going to have to shore them up."
Tuesday's reapportionment announcement will trigger the shuffling of about 12 seats among 18 states, with pickups likely in warm-weather states such as Florida, Georgia, Nevada, South Carolina, and Texas. Ohio is the likely loss leader, with the expected elimination of two congressional districts, followed by New York, which also could lose two seats. Among the states in line to lose one seat: Iowa, Massachusetts, New Jersey, and Pennsylvania.
The bigger the change, of course, the greater the opportunity for the party in power to pursue its interests. But other factors could interfere with GOP plans.
- South Carolina, where Republicans ran the board in both the executive and legislative branches, could add a seventh House seat. The GOP would like to solidify the hold of newly elected Republican Rep. Mick Mulvaney, who defeated 14-term Democratic Rep. John Spratt last month, giving the GOP a seven-to-one edge in the Palmetto State's congressional delegation. An additional seat would tempt the GOP to up the margin. As the Cook Political Report's David Wasserman noted last week, however, a Democratic Justice Department will be monitoring the redrawing and could veto Republican plans based on the Voting Rights Act, arguing instead for the creation of two African-American districts, which would tend to be more favorable to Democrats
- Another instance where the legal pressure to increase minority representation in Congress might tie the GOP's hands: Texas. Republicans control the House, Senate, and governorship, giving them virtual autonomy over map-drawing in a state that could gain as many as four seats. How much the GOP can expand the 23-to-nine advantage it will enjoy next year in the congressional delegation is open to question because the state's demographic growth has been fueled by Latinos. Complying with the Voting Rights Act's mandate will make it hard for Republican redistricting officials to create more GOP districts without unbalancing their incumbents' voter base.