WASHINGTON (AP) — Senator Luján of New Mexico returned to Congress on Thursday for the first time since he had a stroke, which kept him away from Washington for weeks and temporarily weakened Democrats’ hold on power in the equally divided Senate.

Mr. Luján received a standing ovation as he entered a morning hearing of the Senate Commerce, Science and Transportation Committee and was greeted with hugs and fist-bumps from senators later as he stood on the Senate floor during votes.

Teary-eyed, he thanked colleagues at the morning hearing for their support and told them: “It’s an absolute honor to be back.”

“Every one of you that sent me notes, that sent videos, and all the prayers — it worked,” Mr. Luján said.

Mr. Luján, 49, began experiencing dizziness and fatigue on January 27 and checked himself into a hospital in Santa Fe, New Mexico, his office said. He was diagnosed as having had a stroke in the cerebellum and he had surgery to ease swelling in his brain.

His sudden absence had put new strain on Democrats’ fragile 50-50 majority in the Senate, leaving them without full day-to-day control of the chamber and putting President Biden’s legislative agenda and Supreme Court nomination in doubt. But Mr. Luján, in a video message in February, vowed to return after a few weeks of recovery at an inpatient rehabilitation facility.

The senator is expected to resume a fairly normal Senate schedule, participating in hearings and floor votes, as he returns to work.

In a 50-50 Senate, Mr. Luján’s vote could prove critical if Democrats have to confirm Mr. Biden’s Supreme Court nominee without the help of Republicans. His return could also help jump-start work on other legislation and nominations that Republicans oppose.