Updated 6:28 p.m. | Senate Appropriations Chairman Thad Cochran announced Monday he will resign from the chamber effective April 1, giving way to a special election in November. 

“I regret my health has become an ongoing challenge,” the Mississippi Republican 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,” said Cochran, currently in his seventh term.

Senate Majority Leader Mitch McConnell praised Cochran’s leadership in a statement Monday.

“Thad knows there’s a big difference between making a fuss and making a difference. And the people of Mississippi — and our whole nation — have [benefited] from his steady determination to do the latter,” the Kentucky Republican said.

Watch: The Language of Congress — What’s the Difference Between Resigning and Retiring?

Appropriations Vice Chairman Patrick J. Leahy said he was “devastated” by Cochran’s announcement.

“I assumed we would serve out our time together here,” the Vermont Democrat said. “We’ve been like brothers when we traveled. We’ve never once had a partisan word between us. And he has always, always, always kept his word. And I wish to heck some other senators around here would learn to do that.”

Recent strains

Cochran, now 80, served three terms in the House before being elected to the Senate in 1978. While he wouldn’t have been up for re-election until 2020, his health issues had sparked chatter about him leaving the Senate sometime this spring. 

The longtime lawmaker barely won the GOP nomination in his 2014 re-election bid. He failed to secure a majority in the June primary, finishing second behind state Sen. Chris McDaniel, but then narrowly won the runoff later that month.

McDaniel had been waiting to see what Cochran was going to do this year. Just before last week’s filing deadline, he launched a primary campaign against Mississippi’s junior senator, Republican Roger Wicker. But McDaniel has left the door open to switching to a special election race for Cochran’s seat.

It now falls on Republican Gov. Phil Bryant to appoint an interim senator and then call a special election, which would coincide with November’s general election, for the remainder of Cochran’s term. With no primaries for the special election, all candidates will run on one ballot and the race will go to a runoff if no one clears 50 percent. 

Bryant said Monday on Twitter that Cochran’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. 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.

— Phil Bryant (@PhilBryantMS) March 5, 2018

Bryant could choose to appoint himself to the seat — and President Donald Trump and McConnell have reportedly suggested it to him — but local reports last month indicated the governor wasn’t interested. Among the front-runners for the appointment are Lt. Gov. Tate Reeves, Mississippi Secretary of State Delbert Hosemann and state Commissioner of Agriculture and Commerce Cindy Hyde-Smith. 

Health issues

Cochran oversaw the markup of eight of the 12 annual appropriations bills during fiscal 2018. But he has not held a hearing or markup since September of last year — just before he left Washington for a month to address a “urological issue.”

After returning to the Senate in October, Cochran appeared frail, missed votes intermittently as he continued to recover and communicated solely through statements sent out by spokesmen.

Committee staff scheduled markups for Homeland Security and Interior-Environment spending bills, but later canceled “due to the uncertain timing of votes on the budget resolution and expected consideration of the supplemental appropriations bill.”

After weeks of silence about what would happen with those bills, as well as the Financial Services and Defense spending measures, the committee released bill text in November, but markups were not held.

All of those bills are being rewritten, after congressional leaders and the White House reached an agreement in February to raise spending levels for fiscal years 2018 and 2019. 

Last month’s budget legislation also contained a stopgap funding measure — the fifth of the current fiscal year, which began Oct. 1 — running through March 23 to buy appropriators time to write the 12-bill fiscal 2018 omnibus.

Appropriations successor

How the Senate Appropriations Committee will be reorganized following Cochran’s departure remains to be seen. Alabama Republican Richard C. Shelby is widely expected to become chairman. Senate Majority Leader Mitch McConnell has more seniority than Shelby, but it’s highly unlikely the Kentucky Republican would take the gavel.

Following Cochran’s announcement, Shelby told Roll Call he had just spoken with the senator and his wife, Kay.

“Cochran’s been a good friend of mine, 32 years in the Senate,” Shelby said. “I wish him well.”

He said he was well aware of the work that awaits for fiscal 2019, following Cochran’s departure.

“I was ranking [member] before, so I understand. We’ll go to work,” Shelby said.

Whether Shelby will keep leading the Commerce-Justice-Science Appropriations Subcommittee remains to be determined. Alabama has significant defense interests, including the Army’s Fort Rucker and Redstone Arsenal, as well as several defense firms, which might make that an attractive perch for Shelby.

Also up in the air is the chairmanship of the Defense Appropriations Subcommittee, which Cochran will also be relinquishing. 

Niels Lesniewski contributed to this report.