Sen. Max Baucus (D-Mont.): Stepped down as chairman of the Finance Committee in February to serve as U.S. ambassador to China, but he had already announced plans to retire.
Sen. Tim Johnson (D-S.D.): He leads the Banking Committee and is retiring after three terms.
Sen. John D. Rockefeller IV (D-W.Va.): Current leader of the Commerce and Transportation Committee, he's leaving Capitol Hill after five terms.
Rep. Dave Camp (R-Mich.): Retiring after winning his first congressional term in 1990.
Rep. Howard "Buck" McKeon (R-Calif.): After 11 terms, he's term-limited out of his job atop the House Armed Services Committee.
Rep. Mike Rogers (R-Mich.): Stunned colleagues last week by announcing that he'll step down after this year to host a nationally-syndicated radio show. He had two more years to go as leader of the panel.
There's basically two things at work here: Advanced age or term limits on chairmen.
Among the senators, this year's retiring class definitely outranks previous cycles in terms of years of service. All five retiring Democrats have served since in Congress since the late 1970s or 1980s. Baucus and Levin are leaving after 36 years each, while Harkin and Rockefeller will have served 30.
Democrats have less strict rules about how long someone can sit atop a committee, but House Republicans strictly abide by six-year limits, with very few exceptions. Camp, Hastings and McKeon are all at the end of their six-year chairman terms and once they step down, there's little room left for professional growth in the House. Rogers's term atop the intelligence panel doesn't end until 2016, but it appears he's opting instead for a big radio pay day.
Adding to the intrigue, all four retiring chairmen are close friends of Speaker John A. Boehner (R-Ohio), so their exits continue feeding speculation that the House leader also plans to retire after this year.
Overall, this year's retirements are keeping pace with the 2012 cycle but are running ahead of the 2010 cycle. So far, more House Republicans than House Democrats are stepping down, while more Senate Democrats than Senate Republicans are planning to go. Seems that being a member of the majority party has another benefit: If the timing is right, you can leave on top.