Aaron Blake reports that Kansas Republican Senator Sam Brownback will not be running for reelection in 2010: Not in 2008 anymore: 2010 contest for Kansas Senate heats up in a hurry..
Brownback has a extraordinary record on trade. Cato indicates that, since 1997, he's voted against trade barriers 91% of the time. Not only that, he's opposed trade subsidies 69% of the time.
Chris Cillizza lists the candidates lining up to take his place (Friday Senate Line: The 2010 Landscape):
Kansas (R): Sen. Sam Brownback (R) is planning to leave the Senate after two terms to make a run for the open governor's office in 2010. Gov. Kathleen Sebelius
(D), who will be term limited out of office in 2010, is seen as a
leading candidate to run for Brownback's seat and may well be the only
Democrat who can make it a legitimate takeover possibility. (If
Sebelius -- a close ally of Obama -- takes a job in the new
Administration, Democrats have next-to-no chance of winning this seat.)
On the Republican side, Rep. Jerry Moran has already announced he is running to replace Brownback and Rep. Todd Tiahrt -- among others -- is considering the contest.
Cillizza provides overviews of nine other 2010 Senate races. Wikipedia has also set up its 2010 Senate races page: United States Senate races: 2010.