On a tense day on Capitol Hill, Ed Markey became the junior U.S. senator from Massachusetts. Markey took the oath Tuesday morning.

Massachusetts’ U.S. Sen. Elizabeth Warren and the outgoing interim senator, Mo Cowan, escorted Markey into the chamber. Vice President Joe Biden administered the oath.

Markey nearly had to cast a vote on the so-called nuclear option over stalled presidential nominees. But a last-minute deal appeared to hold off the procedural showdown.

Earlier in the morning, Majority Leader Harry Reid gave Markey a less than ceremonious welcome.

“I know a lot of people want to say some real nice things about this man, but you’re going to have to do it later,” Reid said to laughter. “We have a lot of things to do here, and as he will learn the Senate is not always as punctual as the House.”

Markey spent more than 36 years in the House before winning a special election last month to complete the term started by Secretary of State John Kerry.

To keep the seat for a full term, Markey will have to win it again next year.