Former Republican senator Larry Pressler will run for the Senate in South Dakota again, this time as an independent, he announced Thursday, officially inserting a new dose of uncertainty into a race that represents the GOP's best pickup opportunity.
Pressler served in the Senate from 1979 to 1997. He is a moderate who supported President Obama in 2008 and 2012.
The former senator joins a field that includes front-running former governor Mike Rounds (R) and Democrat Rick Weiland, among others. Pressler's history of winning over Republican voters could be a cause for concern for Rounds, who right now stands as the clear favorite in the race for retiring Democratic Sen. Tim Johnson's seat.