CLEVELAND – Vice President-elect JD Vance resigned his Senate seat at midnight Thursday, clearing the way for his swearing-in alongside President-elect Donald Trump on Jan. 20.

Vance, R-Ohio, informed Ohio Gov. Mike DeWine, who will choose his successor, of his plans in a letter Thursday afternoon.

“To the people of Ohio, I would like to express my heartfelt gratitude for the privilege of representing you in the U.S. Senate,” Vance, who has served in the chamber for two years, said in a statement first shared with NBC News. “When I was elected to this office, I promised to never forget where I came from, and I have made sure I keep that promise every day.”

Vance added that voters gave “an undeniable mandate to put America first both at home and abroad” and pledged to work with Trump over the next four years to “execute his agenda.”

Vance, the author of “Hillbilly Elegy” and a former venture capitalist, emerged as a political player in Ohio three years ago when Sen. Rob Portman, a Republican, announced his retirement. Vance competed in a crowded GOP primary filled with better-known and better-funded candidates, but won with Trump’s support.

Now, at 40, he will be the third-youngest vice president in history, behind John Breckinridge (36 years old when he took office in 1857) and Richard Nixon (40 years and 11 days in 1953).

DeWine, a Republican, will choose a replacement who will serve at least until a special election in 2026 to determine who will fill the remaining two years of Vance’s term.

DeWine’s lieutenant governor, Jon Husted, has emerged as the leading candidate but has not yet decided whether to accept the post.

Other Republicans on the short list include former Ohio GOP Chairwoman Jane Timken, Rep. Jay Edwards and state Treasurer Robert Sprague. DeWine and Husted met with Trump at his Mar-a-Lago resort in Florida last month, but sources told NBC News that Trump has made no commitments to Husted, who is campaigning to succeed DeWine amid Senate speculation has prepared, who is temporary as governor.

“I’m not ready to make an announcement yet, but the announcement will be made soon,” DeWine said at a news conference with Husted at the Ohio Statehouse on Wednesday.

Husted told reporters at the news conference that he was “considering all options.”

Hayley Carducci, a spokeswoman for Husted, said Thursday that Husted had no further comment.

DeWine spoke to reporters Thursday evening about the Senate vacancy while attending an event with Trump and other GOP governors at Mar-a-Lago.

“We’ve certainly been working on this for some time and I’ll probably make an announcement next week,” DeWine said.

Asked what Husted thinks about the possibility of an appointment, DeWine declined to reveal details of their conversations.

“Well,” he said, “I won’t go into that tonight.”