How Biden reelection could open door for 10-year presidency of Kamala Harris

If President Biden wins reelection in 2024 and decides not to serve his full four-year term, it could open the door for up to 10 years of a Kamala Harris presidency.

The possibility of Biden leaving office before the conclusion of a second term was the subject of an exchange at the White House briefing on Tuesday. Biden and Harris formally announced their 2024 reelection campaign in the morning.

Should Biden serve half of his second term or more before handing the reins over to Harris, she could serve for the rest of his term and run for president at the top of the ticket in 2028. She could also run again in 2032 for another four-year term.

If Biden serves less than half of a second term, Harris could only run once at the top of the ticket and serve only one four-year term, per the 25th Amendment of the U.S. Constitution. Biden would be 86 at the end of his second term, and Harris would be 63.

A correspondent asked White House Press Secretary Karine Jean-Pierre on Tuesday if Biden intends to serve a full second term if he is reelected in 2024.

"That's something for him to decide," she responded. "I'm just not going to get ahead of the president."

Jean-Pierre followed up on the exchange in a Twitter post after the briefing concluded.

"As you know, we take following the law seriously," Jean-Pierre wrote on Twitter. "So I wanted to be sure that I didn't go into 2024 more than is appropriate under the law. But I can confirm that if reelected, @POTUS would serve all 8 years."

Historian Craig Shirley compared the possible scenario of a vice president finishing a president's term and running on their own twice to the presidency of John F. Kennedy.

Kennedy's vice president, Lyndon Johnson, took over after his death in 1963 and ran successfully for president in 1964. He was eligible to run again in 1968, but he declined.

"We've learned long ago in American politics anything is possible," Shirley said.

"So, yes, it's quite possible with Kamala Harris, but for her to be elected in her own right, God will have to drop everything else," he added, referring to Harris' low approval ratings.

Shirley also said that Biden could temporarily step aside as president and let Harris take over as a test run.

He said Biden could "take a leave of absence from the presidency and make her acting president" like former President Ronald Reagan did twice. He noted that Reagan "handed over the reins of power" to his vice president, George H. W. Bush, for medical reasons.

Reagan finished his second term, and Bush ran successfully for president in 1988. He lost reelection in 1992 to former President Bill Clinton.