According to Senate rules, parliamentarians serve at the pleasure of the body’s majority leader. Senate Parliamentarian Elizabeth MacDonough was appointed in 2012 by Democratic Senate Majority Leader Harry Reid. There have only been six parliamentarians since the position was created in 1935.
While uncommon, a parliamentarian has been fired before. In 2001, Majority Leader Trent Lott dismissed Senate Parliamentarian Robert Dove. Republicans were angry that Dove, a Republican appointee, disallowed spending measures for violating Senate rules.
The House and Senate each have a parliamentarian to assist with questions about the “meaning and application of that chamber’s legislative rules, precedents and practices.” The presiding officer usually accepts the parliamentarian‘s interpretations, but they aren’t binding. A majority vote by the Senate can override the rulings.