Bill Clark, CQ Roll Call via AP

U.S. Sen. Thad Cochran, who has battled several health ailments in recent weeks, will resign April 1, his office announced on Monday.

“I regret my health has become an ongoing challenge,” Cochran said in a release. “I intend to fulfill my responsibilities and commitments to the people of Mississippi and the Senate through the completion of the 2019 appropriations cycle, after which I will formally retire from the Senate.”

Cochran has been the subject of speculation about his health from his last re-election campaign in 2014.

Gov. Phil Bryant, who will select Cochran’s immediate successor, tweeted: “Today, one of Mississippi’s greatest public servants shared with me his plans to retire. @SenThadCochran’s service ushered in an era of unprecedented influence for our state and will benefit generations to come.”

“He was a leader in Washington and a powerful advocate for every Mississippian,” Bryant said in another tweet. “I will always be grateful to Sen. Cochran for his friendship and support during my time of service. Deborah and I wish him and Kay the very best as they begin this new chapter.”

The announcement, while not unexpected given Cochran’s health issues, caught many by surprise with its timing.

“I’m at peace because Sen. Cochran’s at peace,” said his chief of staff, Brad White. “He called me over to his house about two hours ago. We sat down with his wife. He was engaged and asking questions and we talked about timelines. He made his decision, and we rolled it out.”

“This morning when I came to work, I had no idea this was how it would roll out,” White added. “I’m very happy he’s going out his way on his own terms. It’s been the greatest honor of my life.”

The 80-year-old senator was first elected to the Senate in 1978 and is the longest serving current member of Congress. As chairman of the Senate Appropriations Committee, he steers hundreds of millions in federal dollars to Mississippi each year.

Gov. Phil Bryant will have 10 days from April 1 to appoint a temporary office holder, and Mississippians will vote in a special election on Nov. 6 to fill the seat for the remainder of the term, which ends in 2020.

As speculation has grown in recent months about the possibility of Cochran stepping down, Bryant is among those who have been mentioned as potential successors. The governor could appoint himself, or he could resign with the expectation that Lt. Gov. Tate Reeves would move up to the governor’s seat and appoint him. Reeves and Secretary of State Delbert Hosemann are other potential candidates to fill the seat.

Last week, state Sen. Chris McDaniel, R-Ellisville, announced his candidacy for the Senate seat currently held by Sen. Roger Wicker. Afterwards, he did not rule out dropping out of that race and running for Cochran’s seat if it became vacant.

“At this stage, we’re like everybody else in this state,” McDaniel said shortly after the news broke on Monday. “We’re just watching the events unfold, trying to determine what will happen tomorrow. Nobody knows.

“You never want to foreclose options in politics,” McDaniel continued. “But at the same time, we’re running a race against Roger Wicker. We like that race because we’re very different candidates. He has a very different record than I do, and I’m looking forward to him debating me at some point on his record. I’m excited about that race right now.”

State Rep. David Baria, D-Bay St. Louis, also praised Cochran while indicating he will stay in the race for Wicker’s seat: “As a Mississippian, I appreciate all of the years of service that Senator Cochran has provided to our state. I have announced that I am running for the Senate seat currently held by Roger Wicker and have been humbled by the outpouring of support that I have received. I am focused on winning the race that I have entered.”

Reacting to Cochran’s announcement, Trent Lott, a former U.S. Senator from Mississippi who resigned in 2007, said: “I hate it for his sake because I know he loved the job, and he’s done an awful lot of good for Mississippi. He’s earned his retirement, and we owe him a great debt of gratitude. He loves the job, and he’s tough. If he wasn’t having those health issues, he’d have hung in there.”

Rogelio Solis, AP

“Senator Cochran’s service to our nation has made the lives of Mississippians better, and his support of our military has made America safer,” Reeves said in an emailed statement. “He fought relentlessly for Mississippi from helping our farmers get their crops to market to fighting for our citizens after Hurricane Katrina devastated much of the state.

“He earned and maintained the respect of his colleagues on both sides of the aisle even though he never shied away from a battle to protect his beloved state,” noted Reeves. “Elee and I wish Senator Cochran and his family well as they enter this new chapter.”

Rep. Steve Palazzo emailed a statement: “I am thankful that I have been able to work alongside Senator Cochran over the last eight years. The state of Mississippi is fortunate to have a devoted leader like Thad Cochran serving as our Senator. His dedication to making a difference, not only for the state of Mississippi, but the entire nation will be remembered forever. He is someone that has made a permanent impact on our country.”

Cochran has carried on a tradition of Mississippians serving record tenures in the upper chamber. Three senators from the Magnolia State – John Stennis, Jim Eastland and Cochran – are among the 16 longest-serving senators in U.S. history.

And Mississippi, which relies more on federal dollars than any other state in the nation, has a long record of outsized influence over federal spending. Cochran served as Appropriations chairman from 2005-2007 and has served presently since 2015. Stennis served as chairman between 1987-1989. In the House, Rep. Jamie Whitten served as chairman of House Appropriations for a remarkable 14 years from 1979-1993.

Cochran ran successfully for a seat in the U.S. House of Representatives in 1972 at age 34. Four years later, the retirement of longtime Democratic U.S. Sen. James O. Eastland led to a free-for-all, drawing a field of candidates that included former Gov. Bill Waller and civil-rights activist Henry Kirksey on the Democratic side and, among Republicans, then U.S. Rep. Trent Lott and Cochran.

In the general election, Charles Evers, the brother of slain civil rights leader Medgar Evers, ran as an independent finishing second behind Cochran. In capturing the seat, Cochran became the first Republican elected to statewide office in Mississippi since Reconstruction.

Cochran has served on the Senate Ethics, Judiciary, Labor and Human Resources and Indian Affairs committees and chaired the Senate Agriculture, Nutrition and Forestry committees. Since 2014, he has chaired the powerful Senate Appropriations Committee.

In the Senate, Cochran became an expert on agriculture policy and budgets issues and earned note for his acumen in steering money to his home state. In 2005, when Hurricane Katrina ravaged the Mississippi Gulf Coast, Cochran persuaded his colleagues to appropriate nearly $30 billion for the recovery efforts. As a result, Cochran sometimes drew rebuke from pork-barrel-spending watchdogs.

For example, the conservative-leaning Citizens Against Government Waste reported in 2010 that Cochran outpaced all other members of Congress in awarding federal earmarks, a practice that was largely suspended when Republicans regained power in Congress in 2011.

Rogelio V. Solis, AP

Throughout his tenure, Cochran rarely faced serious opposition. Notable exceptions included runs from former Gov. William Winter in 1984 and Democratic state Rep. Erik Fleming in 2008. Cochran faced his most daunting challenge from within his own party against McDaniel during the 2014 Republican primary.

McDaniel, who had wide support from tea party Republicans, criticized Cochran as a longtime Washington, D.C., insider who was insufficiently conservative on social and fiscal issues. McDaniel finished ahead of Cochran in the June 2014 Republican primary, but did not garner enough of the vote to avoid a runoff.

Touting his support for historically black colleges and universities and city infrastructure projects, Cochran drew support from African Americans and others to defeat McDaniel in a runoff election.

Cochran attended the University of Mississippi, graduating in 1959 with a bachelor’s degree in psychology. After college, he joined the U.S. Navy and was stationed in Boston for two years before enrolling in law school at Ole Miss.

During law school, Cochran served as an editor for the Mississippi Law Journal and returned to active duty in the summer months. Afterwards, he practiced law in Jackson starting in 1964, the same year he married the Rose Clayton.

Rose Cochran, who had lived in a nursing home for more than a decade, died in 2014. They had two children: Kate, an English professor at the University of Southern Mississippi, and Clayton, a nonprofit fundraiser who lives in Madison. Cochran married his longtime aide, Kay Webber, in May 2015.

Cochran was born in Pontotoc in 1937 to Emma Grace and William Cochran, both of whom were teachers. In 1946, the Cochran family moved to Byram, a now incorporated community south of Jackson, where the family also raised cattle.

His brother, Nielsen, played professional baseball and served as a Jackson city council member and as a member of Mississippi’s public service commission.

Contributing: R.L. Nave