Sen. Thad Cochran, R-Miss., the ranking member of the Senate Agriculture Committee, leaves a closed-door GOP caucus luncheon at the Capitol in Washington in January. (J. Scott Applewhite/AP)

At 76, Sen. Thad Cochran could have easily retired this year rather than trying to battle through an ideologically divisive primary in pursuit of a seventh term. Instead, the Mississippi Republican decided it was worth the trouble, because he wants another chance at chairing a Senate committee.

“I think it’s very attractive. There are a lot of responsibilities, very serious stuff,” Cochran said of the prospect of a GOP majority and his chance at heading one of two committees on which he has senior status.

Cochran’s rationale makes him something of an outlier these days, a 76-year-old veteran fighting to become a committee chairman when the old order has disappeared and derision abounds for chairmen who consider themselves serious legislators instead of ideological warriors.

Over the past few days, two House Republicans chairing powerful committees announced that they were retiring at the end of the year, joining a pair of House chairmen who have already made the same calculation. That comes on the heels of five Senate Democrats who chaired key panels deciding in recent months not to run for reelection.

The nine retiring chairmen all cited personal reasons, including several in the House who faced internal GOP rules that limit their leadership tenure to three terms atop a committee.

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Taken together, however, the group of chairmen heading for the exits points to the fading glamour of the position. The new calculus seems to be that it’s better to retire in good health than to stick around too long, hoping for one more legislative legacy accomplishment.

But don’t tell that to the Senate Republicans, who have been out of power for almost eight years and have almost no one left in their ranks who knows how to run a committee hearing. Of 45 GOP senators, just 10 have chaired a Senate committee, and several of those had only brief stints in the position before Republicans lost the majority in 2006.

The Senate GOP is so anxious to win back control of committees that some senior senators have publicly declared that they are going to fight with other Republicans to claim the chairman’s gavel of committees they used to rule.

For now, Republicans have set aside those internal disputes to win the majority first, then fight for the gavels after the fact. Those fights, however, are already brewing behind the scenes.

Cochran, who briefly chaired the Senate Appropriations Committee, would like to return to the top post on the panel that controls more than $1 trillion in federal spending each year. Sen. John McCain (Ariz.), who served as the ranking Republican on of the Senate Armed Services Committee, is set on taking control as chairman if his party wins back the majority.

“There’s no controversy,” McCain said Tuesday, asserting that his seniority would vault him to the chairman’s post next year.

The issue is a complex one because Senate Republicans have the most complicated rules on serving as committee leaders.

Democrats in the House and Senate place no limits on the length of time that their members can serve as chairmen or ranking members of the more than 20 standing committees in each chamber. They believe that with seniority comes expertise, leading to lawmakers such as Sen. Carl Levin (D-Mich.) heading the Armed Services Committee for more than 15 years.

House Republicans have the most stringent rules, allowing just six years for any lawmaker to be a chairman or ranking member. So Rep. Dave Camp (R-Mich.), chairman of the House Ways and Means Committee, hits his limit at the end of this year, having served four years as chairman and two as ranking member.

Levin and Camp decided to retire at the end of this year.

Senate Republicans allow their members to serve six years as chairman and six years as ranking member. Because the Senate has alternated majority-party status three times in 13 years, that has made for some potentially uncomfortable disputes over who will be chairmen should Republicans take control in November.

Take McCain. As his caucus’s leading foreign policy and national security expert, McCain waited to ascend to the top slot of the Armed Services Committee. However, that didn’t come until January 2007, when Republicans became the minority party. He served six years as ranking member of the powerful panel, handing off that post to Sen. James M. Inhofe (R-Okla.) 15 months ago.

Having never served as chairman, McCain wants the gavel back and thinks his seniority on the panel will trump Inhofe. “I’ve been deprived,” McCain said, smiling.

Cochran is the ranking Republican on the Senate Agriculture Committee, but only because he hit his six-year limit as ranking member of the Appropriations Committee. In an interview Tuesday, Cochran said he would probably seek to oust Sen. Richard C. Shelby (Ala.), the ranking Republican on the Appropriations Committee, if Republicans claim the majority because Cochran has several years left on his limit to be chairman.

Cochran said he might be able to live with the idea of being agriculture chairman if he is allowed to keep the plum Appropriations subcommittee spot, chairing the defense subcommittee and overseeing nearly $500 billion in annual Pentagon funds.

His first hurdle is clearing a June 3 primary from a conservative challenger who is critical of Cochran’s spending habits as an appropriator.

By tradition, seniority has been the trump card in selecting Senate GOP chairmen, but winning the majority this time would likely lead to internal contests.

Two committee spots are almost certain to remain as is. Sen. Charles E. Grassley (R-Iowa), who has two years left to chair the influential Senate Finance Committee, said Tuesday that he was not likely to try to oust Sen. Orrin G. Hatch (R-Utah) atop the tax-writing panel.