McDaniel, who announced Thursday, begins his quest with support from several high-profile national conservative groups, including Club for Growth, Senate Conservatives Fund and the Madison Project, Roll Call reported.
The seat is considered safely Republican, but Cochran, now in his sixth term, hasn't indicated what he'll do at the end of his term.
McDaniel, who mulled a congressional bid for several months, confirmed his interest in an interview with Roll Call in September.
"I think he will get his head handed to him, and that will be what he deserves," Republican lobbyist Henry Barbour said of McDaniel in the September interview. "[But] it's a free country."
The primary is June 3.
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