AP source: Hillary Clinton to endorse Biden

Hillary Clinton will endorse Joe Biden's presidential candidacy on Tuesday, according to a Democrat who requested anonymity to discuss the plan.

The Biden campaign said Clinton would join the presumptive Democratic nominee for a virtual town hall later Tuesday to discuss the impact of the coronavirus on women. Clinton teased the announcement by tweeting a picture of her, Biden and President Barack Obama laughing in the Oval Office.

As the 2016 Democratic presidential nominee, Clinton made history by becoming the first woman to lead a major party's ticket. Her endorsement is the latest sign of the Democratic Party rallying around its nominee to challenge President Donald Trump in the fall.

Several other leaders from across the party's ideological spectrum have also backed Biden in recent weeks, including Obama, House Speaker Nancy Pelosi and Vermont Sen. Bernie Sanders, a leading progressive.

Hillary Clinton's husband, former President Bill Clinton, has not yet publicly endorsed Biden and has kept a lower profile during the Trump era.

The swift coalescing around Biden stands in stark contrast to four years ago, when Hillary Clinton was unable to win over a significant portion of the electorate's left flank. Sanders battled her to the end of the primary calendar and waged a bitter fight over the party platform before endorsing her and campaigning for her in the fall.

Hillary and Bill Clinton have argued that Sanders' push deeply wounded her campaign against Trump.