Republican House Speaker Paul Ryan will not run for re-election, he announced Wednesday, injecting another layer of uncertainty as Republicans face worries over losing their majority in the fall.

"This year will be my last one as a member of the House," Ryan said. "I will be retiring in January, leaving this majority in good hands with what I believe is a very bright future."

Ryan’s plans have been the source of much speculation and will set off a scramble among his lieutenants to take the helm. A self-styled budget guru, Ryan had made tax cuts a centerpiece of his legislative agenda, and a personal cause, and Congress delivered on that late last year.

Ryan, 48, announced his plans at a closed-door meeting of House Republicans Wednesday morning, according to those present. His tone was somber, and he read directly from prepared remarks.

The speaker called extended family and a few close friends Tuesday night and alerted a few staff. On Wednesday morning, he called the president and the vice president and informed the rest of his staff before going to the conference meeting, officials said.

Ryan will serve out his term and retire in January, Buck said.

Ryan, a Republican from Janesville, Wisconsin, was first elected to Congress in 1998. Along with Reps. Eric Cantor and Kevin McCarthy, he branded himself a rising “Young Gun” in an aging party.

He became the GOP presidential nominee Mitt Romney’s running mate in 2012.

Ryan was pulled into the leadership job by the abrupt retirement of House Speaker John Boehner in 2015. Boehner had struggled to wrangle the chamber’s restless conservative wing and failed to the seal big-picture deals on fiscal policy he sought. Ryan had more trust with the hardliners in the House, but had no more success in brokering fundamental reform of entitlement he sought.

He ultimately had to wrestle with another unexpected challenge: President Donald Trump, a president with little of Ryan’s interest in policy detail or ideological purity. The two have had not had a close working relationship.