McDaniel hadn't ruled out challenging Rep. Steven Palazzo (R ) as well. He told The Associated Press on Tuesday that he was still undecided, but that "right now, we're leaning toward running for U.S. Senate."

McDaniel's staff issued an email to reporters on Wednesday alerting them of his plans to announce his decision on the race at noon Thursday in Ellisville, Miss.

A number of Mississippi Tea Party organizations alerted supporters to McDaniel's announcement on Tuesday, and one is chartering a bus to take members to the announcement, according to the Clarion-Ledger.

Cochran hasn't yet indicated whether he'll run for a seventh term, but is expected to decide by the end of this year.

But McDaniels will likely face difficulty picking up traction in Mississippi, as many prominent Mississippi Republicans expressed their support for the incumbent after he emerged as a possible challenger.