Political analysts at National Journal Hotline predict which senators will face the toughest bids for reelection in 2012, some from primary challengers. We matched those teetering incumbents with their 2010 voting records and found that most are in the moderate wing of their respective parties.
Sen. Bill Nelson, D-Fla.: 42nd most-liberal and 53rd most-conservative voter.
Sen. Scott Brown, R-Mass.: 60th most-liberal and 35th most-conservative voter.
Sen. Ben Nelson, D-Neb.: 54th most-liberal and 41st most-conservative voter.
Sen. Olympia Snowe, R-Maine: 57th most-liberal and 38th most-conservative voter.
Sen. Claire McCaskill, D-Mo.: 47th most-liberal and 48th most-conservative voter.
Sen. Bob Corker, R-Tenn..:68th most-liberal and 27th most-conservative voter.
Sen. Jon Tester, D-Mont.: 52nd most-liberal and 43rd most conservative voter.
Sen. Richard Lugar, R-Ind.:58th most-liberal and 37th most conservative voter.
Exception to the rule: Sen. Sherrod Brown, D-Ohio: Tied for 1st most-liberal voting record, but his seat is in question as his state moves right.
Sen. John Ensign, R-Nev.: 72nd most-liberal and 23rd most-conservative voter.
This article appears in the February 26, 2011, edition of National Journal Magazine.