Sen. Thad Cochran's decision Friday to seek re-election sets up a classic battle between a Republican establishment conservative and an insurgent.
Cochran, who will turn 76 Saturday, was first elected in 1978. He's regarded as one of the Senate's true gentlemen, the top Republican on the Agriculture Committee widely respected by colleagues. He has served as top Republican on the powerful Appropriations Committee.
Cochran's decision to seek another term was reported by the Clarion-Ledger in Jackson, Miss.
Some conservatives have charged in recent years that Cochran has been too eager to spend federal money. State Sen. Chris McDaniel is challenging him for the party's Senate nomination.
Soon after Cochran's decision became public, the conservative Club for Growth made it clear he's in for a fight.
"Republicans in Mississippi have a real choice for the United States Senate this year," said club president Chris Chocola. He called McDaniel "a constitutional conservative with will fight to repeal Obamacare, cut spending and stop President Obama's reckless agenda."