The strong partisan bent of each of the retirees' states means the eventual winner will have best appealed to their bases. North Dakota's congressional delegation included three Democrats for the better part of a generation; now, it's more likely than not to elect a conservative senator. Texas Republicans, some of whom have openly campaigned for Hutchison's seat for more than a year, are fighting over conservative bona fides. And Connecticut Democrats seem headed for a fight among the base in a state that has, in recent years, picked more liberal contenders in primaries.
Conrad, Hutchison, and Lieberman all would have faced competitive reelection bids had they run. Conrad lost two Democratic colleagues in 2010 as North Dakota swung hard right; Hutchison would likely have drawn a primary challenge; and Lieberman would have faced both Democrats and Republicans to hold his seat.
Their departures are but the latest in a steady stream of centrists who have left the Senate. Since 2006, that roster has grown to include Sens. Jim Jeffords, I-Vt., Chuck Hagel, R-Neb., Mel Martinez, R-Fla., Judd Gregg, R-N.H., George Voinovich, R-Ohio, and Byron Dorgan, D-N.D., to name a few. More partisan former members like Sens. Paul Sarbanes, D-Md., Kit Bond, R-Mo., and Bob Bennett, R-Utah, also had bipartisan track records.
Political strategists have learned it is easier to gin up a base than it is to excite the moderate middle. It is easier to play to the worst fears of the left and the right than to compromise.
"In some quarters, 'compromise' has become a dirty word. Senators insist on ideological purity as a precondition," former Sen. Arlen Specter, D-Pa., a centrist who could not win either party's primary, said in his farewell address last year. "It is my hope more senators will return to independence in voting and crossing party lines evident 30 years ago."
Ironically, the rush to partisanship comes at the same time voters tell pollsters they are less partisan than at almost any point in decades. Cumulative data from both Gallup and the Pew Research Center shows those identifying themselves as Democrats and Republicans near historical lows.
But the trend of rampant partisanship is only likely to continue, given the political climate. Sens. Bill Nelson, D-Fla., Ben Nelson, D-Neb., Claire McCaskill, D-Mo., Amy Klobuchar, D-Minn., Jon Tester, D-Mont., Jim Webb, D-Va., and Joe Manchin, D-W.Va., all near the center of the Senate, will face tough reelection battles in 2012. Sens. Olympia Snowe, R-Maine, Richard Lugar, R-Ind., and Orrin Hatch, R-Utah, are all but guaranteed challenges from the right in primaries, threatening the Republicans who have worked most closely with Democrats.
The increased partisan makeup of the Senate is mirrored by the House, though less by retirement than by defeat. Democrats elected moderates and conservatives to swing seats in 2006 and 2008; those members became Republicans' top pickup opportunities, and most of those seats are once again in GOP hands.