Demo­c­ra­t­ic Unit­ed States Sen­a­tor Pat­ty Mur­ray (D‑Washington) has been tapped to take over for retir­ing col­league Patrick Leahy of Ver­mont as the Unit­ed States Sen­ate’s Pres­i­dent Pro Tem­pore in the next Con­gress, her office announced today.

The office of Pres­i­dent Pro Tem­pore is the only posi­tion in the Unit­ed States Sen­ate explic­it­ly men­tioned in the Con­sti­tu­tion of the Unit­ed States.

The rel­e­vant pro­vi­sion of Arti­cle I, Sec­tion 3 says:

The Sen­ate shall chuse their oth­er Offi­cers, and also a Pres­i­dent pro tem­pore, in the Absence of the Vice Pres­i­dent, or when he shall exer­cise the Office of Pres­i­dent of the Unit­ed States.

Pro tem­pore is Latin, and it means “for the time being.”

When the Vice Pres­i­dent is present, they pre­side over the Sen­ate in their capac­i­ty as Pres­i­dent of the Sen­ate. When they are not, the Sen­ate Pres­i­dent Pro Tem­pore fills their role, although the Pres­i­dent Pro Tem­pore is not oblig­at­ed to pre­side over every minute of a Sen­ate ses­sion. In fact, it is com­mon for oth­er mem­bers of the major­i­ty par­ty to pre­side. How­ev­er, the Vice Pres­i­dent or Sen­ate Pres­i­dent Pro Tem­pore usu­al­ly pre­sides on spe­cial occa­sions and for his­toric votes.

The Sen­ate Pres­i­dent Pro Tem­pore is also third in the pres­i­den­tial line of suc­ces­sion, as stip­u­lat­ed in 3 USC § 19, the updat­ed Pres­i­den­tial Suc­ces­sion Act 1947, which pro­vides (as per­mit­ted by the Con­sti­tu­tion): “If, at the time when under sub­sec­tion (a) a Speak­er is to begin the dis­charge of the pow­ers and duties of the office of Pres­i­dent, there is no Speak­er, or the Speak­er fails to qual­i­fy as Act­ing Pres­i­dent, then the Pres­i­dent pro tem­pore of the Sen­ate shall, upon his res­ig­na­tion as Pres­i­dent pro tem­pore and as Sen­a­tor, act as President.”

No one iden­ti­fy­ing as female has ever served in the position.

“Since the office was cre­at­ed in 1789, 91 indi­vid­u­als, from 39 of the 50 states, have served as pres­i­dent pro tem­pore of the Sen­ate,” Wikipedia notes.

All have been men.

Mur­ray will make his­to­ry as the first woman Sen­ate Pres­i­dent Pro Tempore.

“I am hon­ored to have earned the con­fi­dence of Leader Schumer and my col­leagues to serve as Pres­i­dent Pro Tem­pore,” said Mur­ray. “It’s not lost on me the sig­nif­i­cance of what it would mean to be the first woman to serve in this role. I have a great deal of respect for the Sen­ate and the good I am able to accom­plish for fam­i­lies in Wash­ing­ton state as a voice and vote for them.”

“I care deeply about the work we do here in Con­gress and how that work can help the friends and neigh­bors I grew up with and the con­stituents I represent—I look for­ward to the oppor­tu­ni­ty to serve our coun­try in this position.”

The leg­endary U.S. Sen­a­tor War­ren Magn­suon (whose seat is now held by Maria Cantwell, Mur­ray’s seat­mate) is the only oth­er Sen­a­tor from Wash­ing­ton to have held the posi­tion of Pres­i­dent Pro Tem­pore, dur­ing the late 1970s and ear­ly 1980s. Known fond­ly as “Mag­gie,” Mag­nu­son served for over thir­ty-six years in the Sen­ate, an era stretch­ing from 1944 to 1981. For most of those years, he served with Sen­a­tor Hen­ry M. Jack­son, known fond­ly as “Scoop.”

The pow­er­house duo of Scoop and Mag­gie got a lot done for Wash­ing­ton State and the coun­try. Their suc­ces­sors Mur­ray and Cantwell have like­wise accom­plished a great deal, from high capac­i­ty tran­sit invest­ments and weath­er radar deploy­ment to edu­ca­tion reform and finan­cial reform.

Mur­ray will have near­ly matched Mag­nu­son’s lengthy record of ser­vice at the end of the new term she was just elect­ed to if she serves all six years.

Senior­i­ty mat­ters in the Sen­ate. The posi­tion of Pres­i­dent Pro Tem­pore has often been held by the most senior mem­ber of the cham­ber’s major­i­ty par­ty. The cur­rent Pres­i­dent Pro Tem­pore Patrick Leahy of Ver­mont cur­rent­ly has the most senior­i­ty of any sen­a­tor. How­ev­er, as men­tioned, he is retiring.

Cal­i­for­ni­a’s Dianne Fein­stein has more senior­i­ty than Mur­ray and was next in line for the job per tra­di­tion, but Fein­stein is plagued by mem­o­ry issues and has pre­vi­ous­ly said she does­n’t want to serve, prompt­ing Schumer to turn to Mur­ray. The only oth­er sen­a­tors with more senior­i­ty besides Fein­stein are all Repub­li­cans: Chuck Grass­ley, Mitch McConnell, and Richard Shelby.

Mur­ray is expect­ed to remain Assis­tant Leader in the new Con­gress, con­tin­u­ing to serve with Sen­ate Major­i­ty Leader Chuck Schumer and Major­i­ty Whip Dick Durbin.