US Sen. John Thune won't run against Obama in 2012

PIERRE, S.D. The South Dakota Republican told The Associated Press on Tuesday that he's not as well-known and wouldn't be able to raise as much money as other potential GOP candidates. But he's not backing any one person because he doesn't know who will end up in the race.

He also told The AP he sees Obama as a "very shrewd politician" who's moving to the center to attract moderate voters.

Thune says it will take a "fairly unconventional grassroots campaign" to beat the president.

But Thune says he ultimately decided not to run so he can stay in the Senate, where he holds the No. 4 GOP leadership position.