Bernie Sanders has warned that it would be “irresponsible” for his loyalists not to support Joe Biden, warning that progressives who “sit on their hands” in the months ahead would simply enable Donald Trump’s re-election in November. Sanders endorsed Biden on Monday and was quickly followed by the crucial endorsement on Tuesday by Barack Obama of his former vice-president. Meanwhile, Sanders, the 78-year-old Vermont senator confirmed that “it’s probably a very fair assumption” that he would not run for president again, after his failed attempts to win the Democratic nomination in 2016 and in this cycle. He added with a laugh, however, in an interview with the Associated Press: “One can’t predict the future.” Sanders suspended his presidential campaign last week, setting the stage for a November general election battle between two candidates, Trump and Biden, with radically different visions of presidential leadership and America’s role in the world. The contest will unfold in a political landscape transformed beyond all recognition by the coronavirus pandemic that has already claimed at least 14,000 American lives and nearly 10m jobs. On Tuesday night, Sanders criticized his own supporters who have so far resisted his vow to do whatever it takes to help Biden win the presidency. He seemed to distance himself from his campaign’s former national press secretary, Briahna Joy Gray, when asked about her recent statement on social media refusing to endorse Biden. “She is my former press secretary – not on the payroll,” Sanders noted. A spokesman later clarified that all campaign staffers were no longer on the payroll as of Tuesday, though they will get a severance check in May. Sanders said his supporters have a simple choice now that Biden has emerged as the presumptive nominee: “Do we be as active as we can in electing Joe Biden and doing everything we can to move Joe and his campaign in a more progressive direction? Or do we choose to sit it out and allow the most dangerous president in modern American history to get re-elected?” He continued: “I believe that it’s irresponsible for anybody to say, ‘Well, I disagree with Joe Biden’ – I disagree with Joe Biden! – ‘and therefore I’m not going to be involved.’” Sanders said he would not actively campaign or spend money on advertising in the primary contests that are still on the calendar in the coming months. But he still encouraged Democrats in those states to vote for him, hoping to amass as many delegates as possible for leverage to shape the party platform and the direction of Biden’s campaign. He also vowed to continue fighting for progressive priorities such as his signature “Medicare for All” as a senator, even though Biden has refused to embrace the government-backed single-payer healthcare system. “If people want to vote for me, we’d appreciate it,” Sanders said of the roughly 20 primary contests that remain where his name will appear on the ballot. He later added, “I think you’re going to see significant movement on the part of the Biden campaign into a more progressive direction on a whole lot of issues.” Upon gaining his endorsement on Monday, Biden said: “You’ve been the most powerful voice for a fair and more just America. You don’t get enough credit, Bernie, for being the voice that forces us to take a hard look in the mirror.” He continued: “If I am the nominee – which it looks like now you just made me – I really need you, not just to win the campaign but to govern.” Biden has previously said of Sanders’ most fervent supporters “I hear you.” But some progressives are concerned that he is paying lip service more than shifting to the left in his platform. Sanders did not outline any specific plans to begin helping Biden in earnest, though he noted that he held dozens of rallies for former Democratic nominee Hillary Clinton four years ago and would be at least as active for Biden. In the short term, he said he’s essentially “incarcerated in his home” because of coronavirus social distancing guidelines and did not know when he would return to the campaign trail. “I will do everything I can to help elect Joe,” Sanders continued. “We had a contentious campaign. We disagree on issues. But my job now is to not only rally my supporters, but to do everything I can to bring the party together to see that [Trump] is not elected president.”