The midterm elections of 2010 will be unusually high-profile for a number of reasons (term-limited governors, impending redistricting, test of Obama's popularity, attempt to revive the GOP, etc.), and that's not even knowing what we're in for with the economy, Iraq, and God knows what else in the next two years.
In particular, many of the most populous states are headed for multiple big-titan clashes in the statewide, multimillion-dollar-budget races for governor and US senator.
Because of term limits, California will face a wide-open gubernatorial race to succeed Arnold; if, as many expect, Dianne Feinstein runs for that office, it opens up a simultaneous full-throttle race for her senate seat. In Texas, Kay Bailey Hutchison is widely expected to challenge Republican governor Rick Perry in a barn-burner primary -- which again would create an open US senate race that will draw big, big names (with big, big money). New York will have David Paterson's first actual run for election to the governor's office he inherited from Elliot Spitzer; he will certainly get a serious challenge, and Rudy Giuliani is rumored to be looking seriously at it. Plus, whoever Paterson names to replace Hillary Clinton in the US Senate will face his or her first test of the voters, and that will surely draw a serious Republican, and quite likely an intra-party challenge as well. Illinois will have a fascinating re-election bid of a shaky incumbent, as well as the Obama-replacement Senate race. Pennsylvania's governor is term-limited out, so that will be a hot one; and the state's US Senate race is already making news, with the apparent interest of Hardball's Chris Matthews in challenging Republican Arlen Specter.
The one possible exception among the most populous states has been Florida. Governor Charlie Christ and Senator Mel Martinez were likely to be challenged, and any major election in a state that size is interesting, but there was no obvious marquee value yet.
That changed today, with Martinez's announcement that he will not seek re-election. That's got the rumors already flying about who might jump into the race, on both sides of the aisle. Stay tuned!