(CNN)Sen. Tom Udall announced Monday that he would not seek re-election at the end of his term in 2020, writing in a Medium post that "this Senate seat is not my seat."
New Mexico Sen. Tom Udall won't run for re-election in 2020
"When I first ran for Senate, I promised that I would give my all for the people of New Mexico. And I reminded myself that this Senate seat is not my seat. It is New Mexico's seat," the Democrat wrote on the blogging site.
He continued: "The worst thing anyone in public office can do is believe the office belongs to them, rather than to the people they represent. That's why I'm announcing today that I won't be seeking re-election next year."
While he's leaving the Senate, Udall said that he's "certainly not retiring" from public service and intends to find "new ways to serve New Mexico and our country after I finish this term."
The senator did not go into detail about his future plans, saying only that "without the distraction of another campaign, I can get so much more done to help reverse the damage done to our planet, end the scourge of war, and to stop this president's assault on our democracy and our communities."
Udall is the first Democratic senator of the 2020 cycle to announce his retirement. A pair of Republican senators -- Sens. Pat Roberts of Kansas and Lamar Alexander of Tennessee -- have also announced that they won't seek re-election next year when their terms expire.
Udall's announcement comes amid Democrats' efforts to take the upper chamber after capturing the majority in the House of Representatives in the 2018 midterms. Republicans currently hold 53 Senate seats, and Democrats will need three to four pickups to win the majority in 2020, depending on whether they win the White House and, with it, a tie-breaking vote from the vice president.
Udall has held the New Mexico Senate seat since 2009, and easily won re-election in 2014, defeating his Republican opponent, Allen Weh, by more than 10 points that year. New Mexico has voted Democratic in every presidential election since 1988. In 2016, Hillary Clinton won the state with 48% of the vote, over Donald Trump and Gary Johnson.