The next battle in the civil war within the Republican Party will be fought in Mississippi.

On Friday, six-term U.S. Senator Thad Cochran announced he would run for reelection in 2014, setting up a divisive June primary campaign against state senator Chris McDaniel. Cochran, who turns 76 on Saturday, was long considered likely to retire based on his age, his relatively lackluster recent fundraising, and McDaniel’s candidacy. However, he confounded expectations and set the stage for what will be yet another bruising battle between the Republican Establishment and the Tea Party.

Like Mitch McConnell, who facing his own primary challenge in Kentucky, Cochran was a formative figure in building his state’s Republican Party. He was the first Republican senator elected from the Magnolia State since Reconstruction and an played important role in the state’s transformation from a Democratic stronghold of the Solid South to a deep-red GOP bastion. However, unlike McConnell, Cochran rarely sought the spotlight. While his former colleague Trent Lott became a national figure as Senate Majority Leader, Cochran kept to the background and worked on bringing federal money home. He eventually rose to chairman of the Senate Appropriations Committee and would be in line to resume that position in 2014 if he keeps his seat and the GOP takes control of the Senate. But he may not keep his seat.

Cochran is facing a challenge from Chris McDaniel, a state senator who is backed by right-wing groups like the Senate Conservative Fund and the Club for Growth. McDaniel announced in October that he would be running for the seat and he and his supporters have attacked Cochran for not being sufficiently conservative. In a statement, Chris Chocola, president of the Club of Growth and a McDaniel backer, said “Senator Thad Cochran has done some good things for Mississippi, but he’s also done some bad things. He voted to bail out Fannie Mae and Freddie Mac, voted repeatedly to raise the debt limit by trillions of dollars, and even voted against a resolution that stated Congress has a ‘moral obligation’ to cut spending.” In the past, McDaniel has attacked Cochran as having not been a conservative vote or “conservative champion” as well.

The incumbent is already rallying establishment support though. He received the backing of the state’s other Republican senator, Roger Wicker, and will hold a $5,000-a-head fundraiser next week with McConnell.

The Cochran-McDaniel face-off is the latest major establishment vs. Tea Party showdown in the Deep South. Last month, in a special election in a congressional district on Alabama’s Gulf Coast, former GOP state senator Bradley Byrne narrowly edged Tea Party activist Dean Young.