Sen. Thad Cochran (R-MS) announced he will resign from the Senate on April 1, amid widespread reports of his deteriorating health.

Having been in and out of the Senate in the last year due to a string of health issues, including a nose lesion and a series of urinary tract infections, Cochran has increasingly come to represent what has become the oldest Senate in history. Until now, the Republican senator had said he intended to remain in Congress until the end of his term in 2020.

But under increased scrutiny, he changed course.

“I regret my health has become an ongoing challenge,” Cochran said in a statement. “I intend to fulfill my responsibilities and commitments to the people of Mississippi and the Senate through the completion of the 2018 appropriations cycle, after which I will formally retire from the U.S. Senate.”

A recent Politico article called Cochran, who chairs the powerful Appropriations Committee and oversees billions of dollars in government spending, “frail and disoriented.” The senator, who turned 80 last December and has served in the Senate since 1978, “hasn’t presided over a hearing since early September,” Politico’s John Bresnahan and Anna Palmer wrote.

“It is now clear that the large number of older senators in positions of power is taking a toll on the operations of Washington,” Paul Kane wrote in the Washington Post, after Sen. John McCain (R-AZ), who is battling brain cancer, and Cochran were absent from a series of crucial votes.

It’s rumored that Mississippi Gov. Phil Bryant will appoint state House Speaker Philip Gunn to the seat and schedule a special election to replace Cochran for November — the same day as the general midterm elections.

Sen. Roger Wicker (R-MS) is also up for reelection and is facing Cochran’s 2014 primary challenger, state Sen. Chris McDaniel. McDaniel, an anti-establishment conservative who has been tied to Steve Bannon and has a penchant for wanting to oust traditional Republicans, could drop his challenge to Wicker and instead run for Cochran’s seat in the special election. Last time McDaniel ran, the race became so combative, it resulted in one Tea Party leader’s suicide.

Those close to Mississippi’s governor have said Bryant will not offer McDaniel the seat outright, and that the party is instead looking for someone with name recognition in the state who could beat McDaniel in the special election.

Cochran’s retirement could have an impact on Sen. Roger Wicker’s re-election campaign. Depending on who Bryant appoints, Chris McDaniel could drop his challenge to Wicker and run in the special election. — Sam R. Hall (@samrhall) March 5, 2018

Other top contenders include Lt. Gov. Tate Reeves and Secretary of State Delbert Hosemann.

President Donald Trump won Mississippi by nearly 18 points in 2016 in what’s a usually safe Republican state, but the open Senate seat is also giving Democrats some hope of mounting a challenge, especially after Doug Jones, a Democrat, won in a major Senate election upset in the neighboring state of Alabama. Already, state Rep. David Baria, the state House minority leader, has launched a Senate bid to challenge Wicker.

“This election, coupled with historic wins in Virginia and Louisiana, tells us folks are hearing the Democrats’ message throughout the South and want reasonable voices to lead,” Mississippi Democratic Party chair Bobby Moak said after Jones’s win.