Donald Trump is now the oldest party nominee for president in US history

Joe Biden's age was his biggest liability — now Democrats can flip the script on arguments that Biden was too old to lead and apply them to Trump.

• At 78 years old, former President Donald Trump is now the oldest nominee running for president.
• Joe Biden, 81, dropped out of the race on Sunday and endorsed Vice President Kamala Harris, 59.
• If she becomes the Democratic nominee, Harris' age could be an advantage against Trump.

Now that President Joe Biden has dropped out of the 2024 race, Donald Trump, 78, is the oldest nominee of the two major parties to ever run for president.

Biden, 81, was already the oldest president in US history when he took office at age 78. Vice President Kamala Harris, who Biden endorsed as his replacement on the ballot, is 59. Robert F. Kennedy Jr., 70, is also running a long shot campaign as an independent.

Concerns about the president's age were heightened after Biden's poor performance in the first presidential debate in June, during which he appeared frail and struggled to deliver coherent answers. After weeks of Democratic lawmakers and donors calling for Biden to drop out of the race, he announced that he would not run for reelection and endorsed his running mate.

Though Harris still needs to secure her party's nomination, she is 22 years younger than Biden and 19 years younger than Trump. While Biden's age was his biggest liability, Harris' relative youthfulness could prove advantageous on the campaign trail, allowing Democrats to flip the script on arguments that Biden was too old to lead and leverage them against Trump.

Harris' candidacy also marks a significant departure from the gerontocracy that has long dominated American politics. Under Biden, Congress is the oldest it's ever been. Business Insider's 2022 "Red, White and Gray" investigation found that nearly one in four members of Congress are in their 70s or 80s and that while 50% of Americans are under 40, only about 5% of Congress is also under 40.

Delegates will officially select the nominee at the Democratic National Convention in August, but Harris is already racking up endorsements from power players, including former President Bill Clinton, 2016 Democratic nominee Hillary Clinton, and the chairs of the Congressional Black Caucus.