George Voinovich has never been a conservative favorite, to put it mildly, but reports that he won’t seek reelection in 2010 makes the next round of elections more difficult for Republicans. The senior senator from Ohio was virtually a lock to win reelection regardless of political climate — that is, he would be heavily favored even if Republican fortunes failed to improve significantly between now and 2010. Now there will be an open seat in a swing state that has been trending Democratic and where the Republican bench has been decimated by the last two elections. John Kasich is a possibility, but he has been looking at a run for governor instead.

Retirements cost the Republicans House seats in 2008, where the damage might have been contained if there were fewer open seats to defend. The retirements compounded other problems: it made it even more difficult to recruit other viable candidates and it forced Republicans to spread money, which they were having problems raising, too thin. In 2010, the process already seems to be repeating itself in a challenging Senate environment where Republicans will have to defend the seats they won in 2004.

Of course, Republican fortunes can — and probably will — change between now and then, after two years of unified Democratic control of the elected branches of government. Look how quickly the Rovian “permanent Republican majority” of 2004 gave way to the elections of 2006. But even in this scenario, the retirements could complicate things. Think back to 1996, when the Democrats had a worse year than they otherwise would have because Democratic legislators retired when political conditions looked bleak and weren’t around to take advantage when things shifted back somewhat in the Democrats’ favor.

UPDATE: Quin points to the possible ticket of Kasich for governor and Rob Portman for Senate. It would indeed be a conservative ticket, and it would also avoid a gubernatorial primary between Kasich and Portman.