WASHINGTON — President Biden addressed the nation Wednesday night about his decision to abruptly end his campaign and insisted he will remain president through January despite broad concern about his mental acuity.

“I revere this office, but I love my country more,” the 81-year-old president said in a primetime address from the Oval Office in his first extended public remarks on his decision to step aside Sunday and endorse Vice President Kamala Harris.

Follow The Post’s live blog for President Biden’s first speech since dropping out of the 2024 race

“It’s been the honor of my life to serve as your president, but the defense of democracy — which is at stake — I think is more important than any title.”

The president — who has been largely out of the public’s eye since dropping from the race as he recuperated from COVID-19 — spoke with his scandal-plagued son Hunter, 54, seated to the left of the Resolute Desk.

Biden said he stood down to “unite” the Democrats who had become divided over his cognitive fitness and electability against Republican nominee former President Donald Trump.

“When you elected me in this office, I promised to always level with you, to tell you the truth,” said Biden — despite not directly acknowledging or addressing concerns about his apparent mental decline in his 11-minute address.

“In recent weeks, it’s become clear to me I need to unite my party … but nothing can come in the way of saving our democracy – and that includes personal ambition,” Biden said.

“So I’ve decided the best way forward is to pass the torch to a new generation. That’s the best way to unite our nation.”

“You know, there is a time and a place for long years of experience in public life,” Biden said. “There’s also a time and a place for new voices, fresh voices —yes, younger voices. And that time of place is now.”

Biden ran down a list of lame-duck priorities, including “speaking out to protect our kids from gun violence, our planet from climate crisis.”

“I’m going to call for Supreme Court reform because this is critical to our democracy, Supreme Court reform,” he said. “You know, I will keep working to ensure America remains strong, secure and the leader of the free world.”

Biden hailed some of his major legislative achievements, including COVID-19 and infrastructure legislation from 2021, as well as bills that funded green-energy projects and veteran health care.

“We’re also securing our border,” Biden claimed — despite sequential record-high illegal crossings during his first three years in office. “Border crossings are lower today than when the previous administration left office.”

“In just a few months, the American people choose the course of America’s future. I made my choice. I made my views known,” Biden said — doubling down on his endorsement of Harris, 59.

“I’d like to thank our great vice president, Kamala Harris. She’s experienced. She’s tough. She’s capable. She’s been an incredible partner to me and a leader for our country. Now the choice is up to you, the American people.”

What to know about President Biden's decision to drop out of the 2024 presidential race:

• President Biden announced Sunday he is dropping out of the 2024 presidential race — after weeks of prominent Democrats and donors calling on him to withdraw following his disastrous performance in the first presidential debate.
• In a letter posted on X Sunday afternoon, Biden admitted that it is in the “best interest of my party and country” for him to step down as the Democratic nominee.
• Biden wrote that he intends to serve out the remainder of his term and will address the country on his decision later this week.
• In a follow-up X post, Biden endorsed Vice President Kamala Harris for the suddenly open Democratic nomination. “Today I want to offer my full support and endorsement for Kamala to be the nominee of our party this year,” the president wrote.
• Former President Donald Trump reacted to the news by labeling Biden the “worst president in the history of our country” in a call with CNN.

Biden cited the words of Founding Father Benjamin Franklin after emerging from the Constitutional Convention in 1787 that the country would be “a republic, if you can keep it.”

“When Ben Franklin was asked, as he emerged from the, the, the convention going on, whether the founders have given America a monarchy or a republic, Franklin’s response was, ‘A republic, if you can keep it.”

Biden contended that Harris must defeat Trump, 78, saying, “Whether we keep our republic is now in your hands.”

Biden appeared more coherent and rested than he has in weeks, speaking clearly while reading from a teleprompter. He appeared unusually tan, with his white hair slicked back and into place.

“I hope you have some idea how grateful I am to all of you,” Biden concluded. “The great thing about America is here, kings and dictators do not rule, the people do. History is in your hands.”

House Speaker Mike Johnson (R-La.) and other top Republicans are demanding that Biden resign as president due to concerns about his mental fitness, which had prompted leading Democrats including former House Speaker Nancy Pelosi (D-Calif.), Senate Majority Leader Chuck Schumer (D-NY) and former President Barack Obama to all but force him to retire, pointing to bleak polling.

Republicans have taken aim at Harris by arguing she likely knew about and concealed Biden’s decline before his dismal June 27 debate performance, which set in motion the Democratic rebellion against him.

Trump has continued to blast the outgoing president, saying at a rally in Charlotte, NC, moments before Biden’s speech that “Biden doesn’t know he’s alive.”

White House press secretary Karine Jean-Pierre claimed earlier Wednesday that Biden was perfectly capable of serving a second term and that health concerns played no part in his exit — despite Biden himself saying days before his decision that only a medical diagnosis could persuade him to step aside.

“Look, he didn’t step down from campaigning or from running because he didn’t believe he can serve in a second term. That is not why,” she said — insisting too that there was no “coverup” of Biden’s cognitive issues, despite widespread perception to the contrary.