Senator Thomas R. Carper, a veteran Democrat from Delaware, announced on Monday that he would not seek re-election next year, opening up a seat in a deep-blue state that he said he hoped would go to his handpicked successor.
Mr. Carper, 76, is in his fourth term in the Senate and is the last surviving Vietnam veteran to serve there. He has held public office since the 1970s, first as Delaware’s treasurer, then for a decade as a congressman, then as governor and, since 2001, as a senator.
“This just seems like a good time just to turn the page and move on,” Mr. Carper said at a news conference in Wilmington, Del. He added, “I’ve got miles to go, and I’m going to make every day count.”
The senator said he intended to do all he could to help Representative Lisa Blunt Rochester, the Democrat who serves as the state’s only member of the House and was his former intern, win the race to succeed him.
As the chairman of the Environment and Public Works Committee, Mr. Carper said he planned to spend his final months in Congress overseeing the clean energy provisions in the Inflation Reduction Act and key projects included in the bipartisan infrastructure legislation.
“I’ll continue working 60-hour weeks,” he said.
Mr. Carper said he also planned to help his friend President Biden succeed and win re-election, brushing aside questions about the president’s age.
“Every meeting I’ve been a part of, he’s actually sharper than the rest of us,” Mr. Carper said.
He said he had called Ms. Blunt Rochester on Monday morning and told her, “You’ve been patient waiting for me to get out of the way, and I’m going to get out of the way.”
He added that he also told her: “I hope you run, and I hope you’ll let me support you in that mission.”
And Mr. Carper said Ms. Blunt Rochester replied, “Yes, I’ll let you support me.”
Ms. Blunt Rochester, who is also in her fourth term, has not yet announced a campaign but has publicly expressed interest in running. In a statement, she praised Mr. Carper as a lawmaker who was “more interested in attending a local Sunday service than doing the Sunday shows, more interested in hearing from his constituents in person than getting clicks online and more interested in the happenings of the day in Delaware than D.C.”
Senator Chuck Schumer, Democrat of New York and the majority leader, spoke by phone with Ms. Blunt Rochester shortly after hearing of Mr. Carper’s decision and told her he “believes she could be a really good senator and he looks forward to sitting down with her soon,” according to Mr. Schumer’s spokesman.
In a separate statement, Mr. Schumer praised Mr. Carper as a “conscientious, hardworking, honorable and effective senator who has done so much for his beloved Delaware and America, particularly in protecting our precious environment and strengthening our transportation systems.”
Mr. Schumer credited Mr. Carper for spearheading important legislation such as postal reform and reducing the effects of methane in the atmosphere.
Senator Chris Coons, also a Democrat from Delaware, said Mr. Carper relied on his background as a former governor during his time in the Senate.
“Tom Carper has also mentored a generation of Delaware leaders,” Mr. Coons said. “From my first race for County Council president, he has encouraged and supported my career in service, acting as a source of advice and encouragement when I needed it most, and as a role model for balancing family and service.”