SIOUX CITY | Former South Dakota Gov. Mike Rounds on Thursday is scheduled to announce whether he’s running for the U.S. Senate.

Rounds, a Republican, in a statement Wednesday said he's planning stops in Pierre, Rapid City and Sioux Falls.

State Sen. Dan Lederman, R-Dakota Dunes, said Rounds will undoubtedly announce that he plans to seek the seat.

"Not only is he running, he is going to be our next U.S. senator from South Dakota," said Lederman, a close friend of Rounds.

State Democratic Party Executive Director Ben Nesselhuf said Wednesday he also expects Rounds to make things official Thursday.

"He's in. He's been in for two months; we've known that," Nesselhuf said.

U.S. Sen. Tim Johnson, D-S.D., has not indicated whether he will run again.

Speculation that Rounds could run for the U.S. Senate followed him to a Union County Republican Party event in Dakota Dunes on Sept. 13, but Rounds didn't use the venue to announce a decision.

Rounds served two terms as governor, through December 2010, and previously was Republican leader in the South Dakota Senate.

Since leaving office due to term limits, he has been a partner in a Pierre insurance company and has been using the Peter Norbeck Political Action Committee to raise money for Republican legislative candidates.

Bob Burns, a professor emeritus in political science at South Dakota State University, said it makes sense for Rounds to get out early in the campaign.

"I think he's probably trying to discourage other Republicans from getting in the primary," he said. "The sooner you get out there and get your organization going, the better deterrent you have."

Burns said Rounds would be "formidable" as a Senate candidate. But Republican U.S. Rep. Kristi Noem, who recently won a second term in Congress, also would be a strong candidate if she chooses to run, Burns said.

Burns also said Johnson remains a powerful force.

"He would be well-financed and could put together a strong organization,” he said. He would certainly be the best hope the Democrats have of holding on to that Senate seat."

-- Kevin Woster, of the Rapid City Journal, contributed to this report.