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 days, 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 since Biden’s glut of March primary victories 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 since argued that Sanders’ push deeply wounded her fall campaign.

Despite overlapping for decades as Democratic heavyweights, the 77-year-old Biden and the Clintons have never been especially close allies. Biden’s nearest alignment with Hillary Clinton came during Obama’s first term, when Biden was vice president and Clinton was secretary of state. Both had sought the Democratic nomination in 2008 — and both were dogged by their 2002 votes as senators in favor of the war powers resolution that President George W. Bush used to invade Iraq in 2003.

Biden suggested in his 2017 book, “Promise me, Dad,” that Obama favored Clinton’s 2016 presidential bid over the possibility of Biden running. With Obama by his side, Biden announced from the White House Rose Garden in 2015 that he wouldn’t seek the presidency the following year.