• New Mexico Sen. Ben Ray Lujan, 49, is in the hospital after suffering a stroke and undergoing surgery, his office said.
• Lujan, a Democrat, is "expected to make a full recovery," his chief of staff, Carlos Sanchez, said in a statement.
• Lujan's recovery and presumed absence from Washington could complicate Democrats' efforts to quickly appoint a successor to retiring Supreme Court Justice Stephen Breyer.

New Mexico Sen. Ben Ray Lujan suffered a stroke last week and underwent brain surgery, his office revealed Tuesday.

Lujan, a Democrat, is currently hospitalized and is "expected to make a full recovery," his chief of staff, Carlos Sanchez, said in a statement. The 49-year-old senator felt dizzy and fatigued early Thursday before being hospitalized and found to have suffered a stroke in his cerebellum, Sanchez said.

Lujan's recovery and presumed absence from Washington could complicate Democrats' efforts to quickly appoint a successor to retiring Supreme Court Justice Stephen Breyer.

President Joe Biden said he expects to announce his nominee by the end of this month. The president has vowed to pick a Black woman to replace Breyer.

Democrats hold a razor-thin majority in the Senate, which is in charge of confirming new justices to the high court. The chamber is split 50-50 between Democrats and Republicans, with Vice President Kamala Harris wielding the tie-breaking vote.

As long as Lujan is absent, Democrats do not have enough members to allow them to confirm a Supreme Court justice on a party-line vote.

Breyer plans to step down in the summer, but he has suggested that the timing of his retirement will be predicated on whether or not his successor has been confirmed.

Lujan's office declined to comment when asked by NBC News when they expect Lujan could return to work.

A White House spokesman did not immediately respond to questions from CNBC about whether Biden was aware of Lujan's condition, or whether there was any sense at the White House of what Lujan's recovery timeline might be.

Lujan "began experiencing dizziness and fatigue" early Thursday morning, Sanchez said. "He checked himself into Christus St. Vincent Regional Hospital in Santa Fe. He was then transferred to UNM Hospital in Albuquerque for further evaluation."

The senator "was found to have suffered a stroke in the cerebellum, affecting his balance. As part of his treatment plan, he subsequently underwent decompressive surgery to ease swelling," Sanchez said.

"He is currently being cared for at UNM Hospital, resting comfortably, and expected to make a full recovery. The Senator's offices remain open and will continue providing constituent services to all New Mexicans without any interruption," Sanchez said.

"The Senator and his family would like to thank the wonderful doctors and staff at both UNM Hospital and Christus St. Vincent Regional Hospital for their excellent care during this time. Senator Luján looks forward to getting back to work for the people of New Mexico. At this time, he and his family would appreciate their privacy, and ask for your continued prayers and well wishes," the chief of staff said.

It takes weeks to even reach the hearing stage after the president submits his or her pick to the Senate. For modern nominees it has taken 41 days on average, according to the Congressional Research Service.

Despite a deeply polarized environment on Capitol Hill, the White House is optimistic that its nominee to the court will secure at least a few votes from Republicans during her confirmation.

But whether Republicans choose to cross the aisle on this vote depends in part on whether Democrats attempt to pass large swaths of Biden's Build Back Better Act on a party line vote.

Should Lujan be unable to return to work, the state's governor Michelle Lujan Grisham (no relation) would appoint his replacement. The governor is a Democrat, and she would all but certainly appoint a Democrat to Lujan's seat.

On Capitol Hill, news of the senator's stroke sent shockwaves through both parties, and quickly raised questions about why it took five days for his office to disclose his condition.

Sen. Dick Durbin, the Democratic Chairman of the Judiciary Committee, had been unaware of Lujan's stroke until reporters told him about it Tuesday afternoon.

"Oh my God," Durbin reportedly responded.