Republican presidential candidate Mitt Romney won a big endorsement today.

South Dakota Sen. John Thune threw his support behind presidential candidate Mitt Romney, Wednesday.

Thune, who considered running for president himself, is the latest big-time Republican to endorse Romney.

"On the issues that I have been fighting for in my campaign -- creating a better business environment, lessening the regulatory burden, and ending Washington's spending addiction -- Sen. Thune has been a leading voice in the Senate," Romney said in a statement.

Thune won his Senate seat in 2004 after beating Democratic leader Tom Daschle.

He said he decided to support Romney because his ideas to restore the country are drawn from a 25 year career as a conservative businessman.

Thune joined Romney at a campaign stop in Des Moines, Iowa, Wednesday.