Jim Bunning, it seems, has finally given in and will not run for re-election to the US Senate. He is the 6th Republican Senator to opt out for 2010, which is an awfully big percentage of the class -- and indeed of the entire GOP caucus.
In fact, it's pretty amazing to look back at the 55 Republicans who held US Senate seats in 2005, and see just how few will remain one full cycle (ie, six years) later.
Of those 55 Senators from 2005, 27 -- nearly half -- will be gone:
1 died (Thomas, WY)
7 retired (Allard, CO; Craig, ID; Lott, MS; Hagel, NE; Domenici, NM; Frist, TN; Warner, VA)
11 were defeated for re-election (Stevens, AK; Coleman, MN; Talent, MO; Burns, MT; Sununu, NH; Dole, NC; DeWine, OH; Smith, OR; Santorum, PA; Chafee, RI; Allen, VA)
1 switched parties (Specter, PA)
6 are not running for re-election in 2010 (Martinez, FL; Brownback, KS; Bunning, KY; Bond, MO; Gregg, NH; Voinovich, OH)
1 is expected to retire later this year (Hutchison, TX)
Plus John Ensign, who is hanging by a thread, could still end up retiring to make it 28.
Of the remaining 27, 12 face re-election in 2010 -- including at least two who are potentially vulnerable: Burr in North Carolina, and Vitter in Louisiana.