Biden’s victory came after the Associated Press, CNN and NBC showed him winning Pennsylvania and gaining more than the 270 Electoral College votes needed to secure the presidency. Trump sought to undermine the outcome, baselessly accusing Democrats of trying to steal the election and claiming victory before the race was called.

Biden’s running mate, California Senator Kamala Harris, 56, becomes the first Black and Indian-American woman to serve as vice president, a glimpse at a coming generational shift in the party. Biden, 77, will become the oldest president-elect in US history and the first to oust a sitting commander-in-chief after one term since Bill Clinton defeated George H.W. Bush in 1992.

Biden won 284 Electoral College votes, according to the AP, which earlier had called Arizona for the Democrat. Several other networks have yet to call Arizona, leaving Biden with 273 Electoral College votes in their counts, still plenty to claim the presidency. But the incoming president’s goal of uniting the country will be made more difficult by Trump’s unfounded allegations of fraud and with control of the US Senate up in the air, awaiting two runoffs in Georgia in January.

If Republicans hold the Senate, Biden’s agenda of tax hikes on the wealthy and corporations and climate-friendly energy policies could be stymied in Congress. Democrats maintained control of the House of Representatives. Biden won back the battleground states of Michigan, Wisconsin and Pennsylvania — the so-called Blue Wall that delivered the presidency to Trump in 2016. Buoyed by the historic turnout, Biden reaped 4 million more votes than Trump nationwide, as of Saturday morning, winning at least 74 million votes to Trump’s 70 million.