In conservative South Dakota, Democrats didn't even field a candidate to challenge Republican Sen. John Thune, who ousted the Senate's top Democrat, Tom Daschle, six years ago.With Gov. Mike Rounds retiring, polls show Lt. Gov. Dennis Daugaard is favored to keep the office in Republican hands. His Democratic opponent is state Sen. Scott Heidepriem.Republican Kristi Noem is challenging Democrat incumbent Stephanie Herseth Sandlin for South Dakota's only U.S. House seat. The winner of the race between the young, female rising stars could have the inside track to become South Dakota's next senator, as Democrat Tim Johnson is expected to retire by 2014. McCain won South Dakota in 2008.