JACKSON, Mississippi — Republicans suddenly find themselves defending two seats in Mississippi this year as they try to maintain their slim majority in the US Senate.

Republican Sen. Roger Wicker is already up for re-election in the deeply conservative state. And 80-year-old Republican Sen. Thad Cochran announced on Monday that he is resigning April 1 because of poor health.

Cochran is just over halfway through a six-year term. Republican Gov. Phil Bryant will appoint someone to temporarily succeed Cochran, and a special election will be in November - the same day as the regular election for the seat Wicker now holds. The winner of the special election will serve until January 2021.

Democrats are running for the Wicker seat, and the open seat is expected to attract several candidates from both parties. Democrat Mike Espy, President Bill Clinton’s first agriculture secretary, says he has a “strong intention” to run. In 1986 he became the first African-American in modern times to win a congressional seat in Mississippi.

Cochran’s departure set off a scramble within a state Republican Party already struggling to manage a disaffected conservative faction. Chris McDaniel, the outspoken, tea party-backed state senator who came close to defeating Cochran in a bitter 2014 Republican primary, qualified last week to challenge Wicker but said he might jump to the special election if the Cochran seat is open. McDaniel said Monday it is “premature” to say what he will do.

Republicans in Washington are hoping to prevent a rough and costly primary season as they struggle to defend their 51-49 hold on the Senate. Some Republicans have doubts about McDaniel’s ability to win a general election. And after Republicans’ bruising loss in Alabama last year, party leaders are eager to block any risky candidates.

Cochran has been a sporadic presence on Capitol Hill in recent months. He stayed home for a month last fall, returning to Washington in October to give Republicans the majority they needed to pass a budget plan. He has since kept a low profile and an aide ever present at his side.

“I regret my health has become an ongoing challenge,” Cochran said in a statement. “It has been a great honor to serve the people of Mississippi and our country. ... My hope is by making this announcement now, a smooth transition can be ensured so their voice will continue to be heard in Washington, D.C.”

Cochran was first elected to the Senate in 1978 after serving six years in the House. A mild-mannered Southerner, Cochran came to the Senate when it had a far clubbier atmosphere and he played an insider’s game throughout his seven terms - particularly as a member of the powerful Appropriations panel, which had long been a bipartisan powerhouse and way to funnel taxpayer dollars back home.

Cochran chaired the committee twice and used the post to channel money to Mississippi and other Gulf Coast states for Hurricane Katrina recovery after the 2005 storm.

“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,” Senate Majority Leader Mitch McConnell said in a statement.

“I’m devastated. I assumed we would serve out our time together here,” said Sen. Patrick Leahy of Vermont, the top Democrat on the Appropriations panel. — AP