JACKSON (AP) — Sen. Thad Cochran of Mississippi will seek a seventh term in 2014, setting up a Republican primary that pits an established incumbent who has brought billions of dollars to his home state against a tea party-backed challenger who says federal spending is out of control.

Cochran, who turns 76 on Saturday, has been in the Senate since 1978. He’s the top GOP lawmaker on the Agriculture Committee and a senior member of the Appropriations panel.

His chief of staff, Bruce Evans, said Friday that Cochran will seek re-election, ending months of speculation about the senator’s plans.

A tea party-backed candidate, state Sen. Chris McDaniel, announced in October that he’d seek the seat, regardless of what Cochran does.

Political scientist Marty Wiseman, director of the Stennis Institute of Government at Mississippi State University, said that Cochran, by bringing big federal dollars to one of the poorest state in the nation, has built a strong base that crosses lines of party, race and geography.

“I have always thought of him as being the most unbeatable politician in Mississippi,” Wiseman said of Cochran.

Many Republicans and Democrats also believe Cochran would be difficult to defeat.

Republicans need to gain six seats in the Senate to regain control after the 2014 elections. Democrats would welcome a polarizing Republican primary in Mississippi because it could help the party compete in a state that has long backed Republicans in federal elections. The last Democrat to win a U.S. Senate election in the state was John Stennis, who served more than 50 years before choosing not to seek re-election in 1988.

With his election to the Senate in 1978, Cochran became the first Republican since Reconstruction to win a statewide office in Mississippi.

Cochran is a past chairman of the Senate Appropriations Committee, bringing billions of federal dollars to the state for military bases, universities, local schools, highways and a wide variety of other projects. The spending has made Cochran many friends and brought sharp criticism from people who see it all as pork.

Cochran has a home in Oxford. He was an Ole Miss cheerleader in the 1960s and is an attorney, piano player and state history aficionado. He’s such a fixture in Mississippi politics that he’s recognizable by his first name.

Cochran has had to break a sweat only once being elected to the Senate: It was during his first re-election campaign in 1984, when he defeated former Democratic Gov. William Winter. Since then, Cochran has easily defeated challengers.

Conservative and tea party groups such as the Club for Growth and the Senate Conservatives Fund have rallied behind McDaniel, pressuring Cochran to retire. Conservatives have criticized Cochran’s support of spending bills, Mississippi projects and his willingness to work with Democrats on some issues. Cochran was the first Republican, for example, to back former Nebraska Sen. Chuck Hagel to be defense secretary.

The Senate Conservatives Action, the super PAC arm of a group founded by former South Carolina Sen. Jim DeMint, has been airing television ads in Mississippi introducing voters to McDaniel and presenting him as an outsider who would curb the federal debt.

Cochran is holding nearly $804,000 in campaign cash. He had raised only about $48,000 from July through the end of September, sparking speculation among some that he planned to retire.