Sen. Bernie Sanders (I-VT) endorsed former Vice President Joe Biden on Monday in an effort to unite the Democratic Party ahead of the 2020 presidential election.

Sanders, a Democratic Socialist who represents the party’s left flank, suspended his presidential campaign last week, clearing the way for Biden to win the party’s presidential nomination.

“We’ve got to make Trump a one-term president and we need you in the White House,” Sanders said to Biden in a livestream Monday.

We must come together to defeat the most dangerous president in modern history. I'm joining @JoeBiden's livestream with a special announcement. https://t.co/AC3zh3ChX3 — Bernie Sanders (@BernieSanders) April 13, 2020

“Bernie, I want to thank you for that, it means a great deal,” Biden said a couple minutes later.

Introducing Sanders, Biden said he aimed to “build a fair, more inclusive more resilient America,” and described his former opponent as “a leader who shares those values and has been an outspoken advocate for that vision for a long time.”

Sanders’ endorsement doesn’t necessarily mean that his supporters will fall in line behind Biden: The two candidates, Monday’s commity aside, maintain different stances on major issues.

Rep. Alexandria Ocasio-Cortez (D-NY), a key Sanders surrogate when his campaign was surging, said in an interview published Monday that Biden would have to make some “uncomfortable” concessions to win her enthusiastic endorsement — though she committed to supporting the nominee.

The COVID-19 pandemic has fundamentally changed the 2020 campaign, and Sanders’ endorsement was no different: Rather than building up to a packed rally, Sanders tweeted that he would be “joining @JoeBiden‘s livestream with a special announcement” just minutes before the two candidates appeared on screen.

What followed was a diplomatic conversation between the pair of septuagenarians, who referred to each other by their first names and hinted at several “task forces” to address policy priorities, including on the economy, education, crimal justice reform, immigration and climate change.

“I promise you I will not let you down,” Biden said at the conversation’s end, before asking if Sanders had anything to add.

“I thought we’d play some chess,” Sanders joked. “What do you think?”