DOVER, Del. (AP) — Democratic Sen. Tom Carper of Delaware announced Monday that he will not seek reelection to a fifth term in the U.S. Senate.

Carper's announcement paves the way for a wide-open contest for the seat he has held since 2001 in heavily-blue Delaware. It also ensures that his unblemished record of never having lost an election during more than four decades in politics remains intact.

"If I ran for a fifth term in the Senate and won, it would be a record 15 statewide elections," Carper, 76, noted in prepared remarks at a Wilmington news conference. He said he and his wife, Martha, began talking months ago about what the future holds for them.

“After a good deal of prayer and introspection, and more than a few heart-to-heart conversations, we’ve decided we should run through the tape over the next 20 months and finish the important work that my staff and I have begun on a wide range of fronts, many of them begun in partnership with Democrat and Republican colleagues in the Senate and in the House,” he said.

Carper is one of several incumbent senators who have announced that they will not seek reelection next year. The others are Democrats Ben Cardin of Maryland, Dianne Feinstein of California and Debbie Stabenow of Michigan, and Republican Mike Braun of Indiana.

Carper said his focus over the next year and a half will be helping ensure implementation of environmental provisions in the 2021 infrastructure law and the Inflation Reduction Act.

“Implementation of both laws is indispensable if we are ultimately to win the battle against global warming while creating tens of millions of American jobs in the years to come,” he said.

Carper served five terms in the U.S. House and two terms as governor before being elected to the Senate in 2000. He began his political career as state treasurer in Delaware. In the Senate, he built a reputation as a moderate Democrat with a strong interest in environmental issues. He also has helped lead efforts to shore up the financially struggling U.S. Postal Service.

“The great privilege of my life has been the opportunity to serve the people of the First State and of the United States in so many different roles for so many years,” he said.

Carper’s last election win came in 2018, when he easily defeated Republican challenger Rob Arlett, who had been Donald Trump’s state campaign chair in 2016. Carper faced off with Arlett after trouncing a progressive challenger in a Democratic primary, stemming an antiestablishment tide hoping to move the Democratic party to the left.