After eight years on the job and 25 years on Capitol Hill, House Parliamentarian John Sullivan will step down March 31.

Succeeding Sullivan will be Thomas Wickham, who has been deputy parliamentarian since 2005. Sullivan also served as deputy before assuming the senior post.

“John Sullivan’s retirement is a loss for the people’s House, which he has served with grace and distinction,” Speaker John Boehner (R-Ohio) said in a statement announcing the changes. “Tom Wickham, in addition to being a master of the House’s rules and traditions, has the sound judgment and steady temperament required to serve as parliamentarian … [and] has earned the respect of lawmakers and staff on both sides of the aisle.”

The House parliamentarian advises the chamber’s leaders and other lawmakers on rules and precedent, sometimes on a confidential basis. Although appointed by the Speaker, the parliamentarian is a nonpartisan position that requires an unbiased interpretation of legislative and procedural rules.

Sullivan, 60, was appointed parliamentarian in May 2004 after the retirement of Charles Johnson, who served in the post for about a decade.

Wickham, 43, began his tenure with the parliamentarian’s office as assistant parliamentarian in 2005.

Sullivan is only the fourth individual to hold the title of parliamentarian — prior to 1927, House officials performed aspects of the parliamentarian’s duties as “messenger to the Speaker” and “clerk at the Speaker’s table.”

Lewis Deshler became parliamentarian proper when the position was created at the start of the 70th Congress — and went on to hold the job for the next 46 years.

William Holmes Brown took over in 1974 and served for two decades before making room for Johnson.

Parliamentarians are expected to advise on the rules of the House without regard to party.

It isn’t always easy, and parliamentarians can find themselves embroiled in partisan disputes. In August 2007, during House floor consideration of an agriculture appropriations bill, a flurry of last-minute vote changing caused confusion over a Republican motion to recommit.

When the clock ran out on an extended vote, the original outcome showed a tie, which would have resulted in the motion’s defeat. But as Members sought to change their votes, then-Majority Leader Steny Hoyer (D-Md.) sought to gavel the vote closed and reportedly exclaimed, “We control the House, not the parliamentarians.”

The incident prompted the creation of a special investigative panel, and Republicans accused Hoyer of undermining the parliamentarian’s judgment.

In his official statement on the occasion of Sullivan’s retirement, Hoyer did not reference that event.

“[He] has been a careful steward of the rules of the House and a strong defender of their proper exercise,” he said.

Other lawmakers also took the opportunity to praise Sullivan.

In a statement, Minority Leader Nancy Pelosi (D-Calif.) pointed to his “keen mind, excellent legal training and commitment to public service to make nonpartisan, objective decisions.”

Rep. David Dreier (R-Calif.) — chairman of the House Rules Committee, which works closely with the parliamentarian’s office — said there was “no more incisive mind in this place than John Sullivan’s.”

“He came with me on a trip to Africa, looked at the Kenyan Constitution, and was able to spot a discrepancy … just like that,” Dreier said with a snap of his fingers.

Daniel Newhauser contributed to this report.