“I have decided to depart the House at the end of this year to serve America in new ways,” McCarthy, 58, wrote in a Wall Street Journal column.
“It often seems that the more Washington does, the worse America gets,” said McCarthy, who was ousted as speaker by hardline Republicans in early October.
“The challenges we face are more likely to be solved by innovation than legislation,” he added.
The departure of the former party leader and campaign fundraising juggernaut, who helped Republicans take control of the House in 2022, could hamper party hopes of retaining that majority next year.
While he represents a safely Republican California district, his departure will further narrow Republicans’ already slim 221-213 majority early next year as Congress tries to avert a partial government shutdown in mid-January.
Under California law, a special election must take place within 126 to 140 days from the time the state’s governor calls it.
McCarthy vowed to continue recruiting candidates for elective office.
“The Republican Party is expanding every day, and I am committed to lending my experience to support the next generation of leaders,” he said.
McCarthy announced his plans a week after the House expelled indicted Republican George Santos from Congress. On Tuesday, another top House Republican, Representative Patrick McHenry, who steered the chamber in the chaotic weeks after McCarthy’s ouster, said he would not seek reelection.
“He did an excellent job, and I think he deserves a lot of credit for us being in the majority. He has had an outstanding career,” said Republican Representative Buddy Carter said of McCarthy. “I don’t think he deserved what happened.”
McCarthy, who first entered Congress in 2007, spent the ensuing years rising through party leadership ranks in the House before beginning a brief but wild term as the top Republican in Congress. He belonged to a rising generation of Republicans known as “young guns,” which included former Speaker Paul Ryan.
His tenure as speaker was marked by stormy relations with Republican hardliners, who forced him to endure 15 humiliating floor votes before receiving the gavel last January.
“When it takes 15 rounds to get elected, you know it’s going to be a rough go,” Carter said.
Hardliners then voted McCarthy out on Oct. 3 after he backed a bipartisan spending measure that averted a government shutdown.
“No matter the odds, or personal cost, we did the right thing. That may seem out of fashion in Washington these days, but delivering results for the American people is still celebrated across the country,” McCarthy wrote.
He was replaced by Speaker Mike Johnson, a relative newcomer to the leadership, after weeks of Republican infighting in which three more seasoned candidates were nominated and then rejected.
McCarthy ran afoul of hardliners when he publicly said that then-President Donald Trump bore responsibility for the deadly Jan. 6, 2021, attack on the US Capitol, days after the violence, though he later repeatedly voiced allegiance to the former president.
McCarthy also drew their ire earlier this year by striking a deal with Democratic President Joe Biden that averted a default on US debt and set a $1.59 trillion spending limit for fiscal 2024. Hardliners shuttered the House floor for days over the spending agreement but have since said they would accept it.
McCarthy was the first US House speaker to be ejected from the chair. But he will become the third Republican speaker, after John Boehner and Ryan, to leave Congress following repeated clashes with the Republican hard right.
He launched an impeachment inquiry into Biden, focused on Biden’s son Hunter Biden’s business dealings, which Democrats have denounced as politically motivated and unsubstantiated by evidence.
McCarthy won reelection in 2022 by a 35-point margin, and his California district is not seen as competitive by the three main nonpartisan election forecasters.
(Reporting by David Morgan; additional reporting by Moira Warburton; editing by Scott Malone, Alistair Bell, Jonathan Oatis and Cynthia Osterman)