Probably a combination of turnout and voters who voted for Holden switching to Blunt.
I haven't did the checking to see if Kinder/Cook (for Lt. Governor) or Carnahan/Hanaway (for Secretary of State) had such results.
I'm sure the maps comparing Blunt (Springfield) v. McCaskill (Kansas City) against Kinder (Cape Girardeau) v. Cook (Cape Girardeau) would be interesting.
Blunt, if he can get though this first term, will probably be on a fast track to running for the Presidency in 2012 or 2016. Something about him makes me think that he could run for President and get a lot of the Fundamentalist support, and establishment support from his dad.
Are Secretary of States elected on the same tickets as Governors in MO? And do you have any idea why his approval numbers are so low?