Politico has a story claiming that Republican Senate sources say Sen. George Voinovich (R-OH) will announce today that he will retire in 2010 and will not run for reelection. If true, this will be the fourth Republican retirement already. The others are Sen. Sam Brownback (R-KS), Sen. Mel Martinez (R-FL), and Sen. Kit Bond (R-MO). This is extremely bad news for the Republicans as all four seats may be seriously in play.
Ohio went to Obama in 2008 and the other senator (Sherrod Brown) and the governor (Ted Strickland) are Democrats. In addition, 10 of the 18 representatives are Democrats, so the Democrats have a good pool to draw on (as do the Republicans). But having this seat go from any easy win to a battle royal is not good news for the Republicans.
Florida is another swing state. Martinez was not a particularly strong candidate, but incumbents always have the edge and now there is an open seat there. Former governor Jeb Bush would have been a very strong candidate, but he has announced that he is not running. Probably the strongest Democrat is Chief Financial Officer (i.e., state treasurer) Alex Sink, but she hasn't announced her plans yet. Even if she runs, she might have to get through a primary with one or more representatives. The Republicans also have a number of representatives who may be interested.
Missouri is also a swing state. While McCain carried the state by under 4000 votes, the Democrats picked up the governorship in 2008 and won a Senate seat by 50,000 votes in 2006. Former senator Jim Talent is said to be interested in a comeback. The most likely Democrat is Secretary of State Robin Carnahan, daughter of former Democratic governor Mel Carnahan, who was elected to the Senate himself in 2000, even though he had died in a plane crash two weeks earlier.
Finally, we come to Kansas, which is a very Republican state. Nevertheless, there is one scenario in which a Democrat could get elected to the Senate here. Namely, if Sen. Sam Brownback (R-KS) runs for governor and Gov. Kathleen Sebelius (D-KS) runs for the Senate. In that case, the voters may perceive it as an even trade: two popular politicians just switching offices.
Currently no Democrats have announced their retirement and none of them really even look vulnerable. 2010 could be the third straight cycle in which the Democrats have the wind at their backs, in part due to psychology. If you were a Republican representative from a safe district, would it be easy to convince you to give up your seniority and safe seat for a 50-50 chance to become a freshman senator in a small and powerless minority? As a consequence of the fact that the Democrats will not only control the Senate after the 2010 elections, but may well have a filibuster-proof majority, it will be tough for NRSC chairman Sen. John Cornyn (R-TX) to recruit top-tier candidates for all the open seats and also for challenging incumbent Democrats. Finally, the prospect of being in a minority with fewer than 40 seats may cause other Republican senators to retire rather than to go through a big fight and have relatively little power even if they win. Potential retirement candidates are Sen. Jim Bunning (R-KY), Sen Arlen Specter (R-PA), and maybe even Sen. David Vitter (R-LA).