It's a Senate first.

For the first time, the Senate parliamentarian will be a woman.

Elizabeth MacDonough, currently the senior assistant parliamentarian, will move into her new role as the chief Senate parliamentarian tomorrow.

It is the first time the job has been filled by a woman since the job was created in 1935.

The Senate parliamentarian is an important and powerful job, put in the spotlight during contentious and partisan debates to interpret complex Senate rules and procedures as legislation makes its way through Congress.

MacDonough replaces the retiring Alan Frumin, who first held the post in 1987 and has served collectively nearly 20 years in the Senate, with a brief hiatus in the late 1990s.

On Frumin's last day in the Senate today, leaders of both parties paid homage to his long and at times challenging career as the so-called "umpire" in the Senate "ballgame."

"It's not an easy job to be an umpire for 100 senators," Senate Minority leader Mitch McConnell, R-Ky., said today on the Senate floor. "It isn't easy to keep up with 200 years of precedents. He never has hesitated to admit when he got something wrong. Alan has a deep love for the Senate and the people who make it work."

Senate Majority Leader Harry Reid, D-Nev., joked that in March 2010 as President Obama's the health care bill was working its way through the Senate, Frumin was cast into the spotlight, maybe more than he wanted to be.

"He was briefly a Washington celebrity," Reid said. "Despite the pressure, despite the national spotlight, Mr. Frumin remained calm and professional through what must have been one of the most tense moments of his career. For a very few weeks, every Capitol Hill reporter knew his name for sure. His respectable face was on every political news blog. Every political science professor talked about him. Even a few folks outside the beltway learned what on earth was a Senate parliamentarian, what do they do?"

MacDonough has worked with Frumin for 10 years and will be the sixth person to hold the job since its creation.

"She steps into very large shoes," Reid said today.

The Senate's controlling party names, or keeps in place, the parliamentarian, so if the Republicans win back control of the Senate in the upcoming election, McConnell could replace MacDonough.