States can be fickle. Some years, a state's voters might go for a Republican for Senate. And in the next election, they may turn around and elect a Democrat. It can make for some truly disparate voting records among a state's Senators. But these "Odd Couple" pairings are volatile, and have a good chance of changing on any given year.
National Journal's most recent rankings include three such pairs, some faced with dramatic breakups in the current Congress and the coming year.
1) Sens. Herb Kohl, D-Wis., and Ron Johnson, R-Wis., topped the charts as the oddest bedfellows this year. Johnson was the fifth-most-conservative member of the Senate this year, while his Democratic counterpart Kohl was the 67th most conservative. But this couple is no more, as Kohl retired at the end of 2012. Wisconsin is still likely to rank among odd couples next year, as Kohl has been replaced by a liberal Democrat, Sen. Tammy Baldwin.
2) Sens. Tim Johnson, D-S.D., and John Thune, R-S.D., rank second overall among divergent same-state Senate pairings. But rumors are swirling that Johnson may not seek another term and could retire in 2014. This could open the door to former Republican Gov. Mike Rounds to take the spot and end South Dakota's time on the Odd Couples list.
3) Iowa Democratic Sen. Tom Harkin's upcoming retirement in 2014 will end a true Odd-Couple power couple. Harkin took office in 1985 and has been a true liberal lion during his time in the upper chamber, while sitting beside Republican Sen. Chuck Grassley, who always ranks among its most conservative members (and has one of the best Twitter feeds around). Whether the seat stays in Democratic hands or goes Republican is very much up in the air.