http://en.wikipedia.org/wiki/Robin_CarnahanThere is a 99.9% chance that Robin Carnahan will run and win.
Here's why:
1) She's in her second term as MO's SOS, but Jay Nixon, a Democrat, is just beginning his first term as Governor. She might have run for Governor in 2012 if Matt Blunt's career hadn't gone down like a cheap hooker, but Jay had the higher profile in state government and so he ran as the Democrat and wiped up the lame candidate the repubs ran. I doubt she wants to wait for Jay to finish two terms as Governor before she runs for it, nor do I think she wants to oppose Claire McCaskill for re-election 2012. The Democratic Party, both state and national, would be crazy to not have her run for Senate in 2010. After Jay, she has the most recognizable name in Missouri, and it's open to debate whether she's not better known here than he is.
2) She's an heir to a well known (in Missouri) political family that is greatly admired by both Dems and Republicans; she was re-elected SOS by a big margin and the Repubs didn't even mount a serious candidate to oppose her. She has good liberal creds but relates incredibly well to those all-important conservative rural voters ("I grew up on a farm...I know bull when I see it."--a 2004 campaign ad).
3) Both her parents were Senators for Missouri, as you all most likely know. She is as big a shoe-in to replace Kit Bond as any individual in this state could possibly be.