One of the few remaining moderate Republicans in American politics, Senator Romney, has announced that he will not seek re-election to the Senate in 2024. In doing so, he also called on Presidents Biden and Trump to step off the stage. 

In a nearly three-minute video posted Tuesday to his government account on X, Mr. Romney said, “at the end of another term, I’d be in my mid-80s. Frankly, it’s time for a new generation of leaders. They’re the ones that need to make the decisions that will shape the world they will be living in.”

Mr. Romney was likely to face stiff opposition from fellow Republicans in his bid to be renominated by his party next year. According to a recent poll from the Salt Lake Tribune, Mr. Romney garnered 30 percent of the GOP primary vote — still beating every hypothetical challenger but historically weak for a sitting senator. At the Utah GOP convention shortly after he voted to convict Mr. Trump in 2021, he was booed by party delegates and was nearly censured. 

Other candidates likely to run for the seat are a former congressman, Jason Chaffetz, and the state attorney general, Sean Reyes. The speaker of the Utah house, Brad Wilson, has formed an exploratory committee regarding a run next year, with a decision expected in the coming weeks. The mayor of Riverton, Trent Stagges, is also running and has been endorsed by Fox News’s Mark Levin and Turning Point USA’s Charlie Kirk. 

In the video posted online, Mr. Romney boasted about the significant legislation he had a hand in crafting during his four-and-a-half years in the Senate, including Covid relief, the 2021 infrastructure bill, and a bipartisan gun control law. 

In the video, Mr. Romney said both the current and former presidents are not taking on America’s most pressing challenges, including confronting Communist China, addressing climate change, dealing with the national debt, and reining in entitlement spending. “Neither President Biden nor former President Trump are leading their party to confront those issues,” he said. 

The Utah senator informed select members of the press of his intention to retire before the announcement was made. In an interview with the Washington Post’s Dan Balz before the video was released, Mr. Romney lamented the dysfunction of Congress and said Messrs. Biden and Trump are “unable” to serve the American people well in the White House. 

“It’s very difficult for the House to operate, from what I can tell,” he said of the chaos currently unfolding in the lower chamber surrounding budget negotiations. “And two, and perhaps more importantly, we’re probably going to have either Trump or Biden as our next president. And Biden is unable to lead on important matters and Trump is unwilling to lead on important matters.”

Mr. Romney had previously agreed to have his biography written by the Atlantic’s McKay Coppins — a fellow Mormon who first met Mr. Romney while covering his ill-fated 2012 presidential campaign. The book, “Romney: A Reckoning,” is due out on October 24. Shortly after the senator’s announcement was posted online, the Atlantic published an excerpt of Mr. Coppins’s book. 

Mr. Romney informed the journalist of his intention to retire earlier this year and spent hours sitting with him late at night in his Senate office and at his townhouse at the nation’s capital. The senator spent many nights eating dinner alone, not having made many friends at the District of Columbia, especially after voting to convict Mr. Trump following his first impeachment. 

“A very large portion of my party really doesn’t believe in the Constitution,” Mr. Romney told Mr. Coppins, wondering aloud if Mr. Trump had irreparably bent the Republican Party in a nationalist, populist direction, or if he and his “establishment” Republican counterparts were simply too naive to see it. 

When he leaves office in January 2025, he will be 78 years old. Elected to the Senate in 2018, Mr. Romney had previously served as governor of Massachusetts for four years and is only the third person in American history to have served as governor of one state and as a senator from another — the others being Sam Houston as governor of Tennessee and a senator from Texas before the Civil War, and John Frémont, who served as one of California’s senators and Arizona’s governor in the late 19th century.