The former vice president's team has been preparing the campaign for months, and Biden's decision is becoming less secretive or exciting by the day. Now that he has given his advisors the green light, Biden faces one of the biggest challenges of his political career, which he has made in his half century.
He is scheduled to hold his first campaign in Pittsburgh on Monday, sources said, and he would go to the early-election states of Iowa, South Carolina and New Hampshire in the coming days.
His political action committee, American Possibilities, sent an email to supporters on Tuesday urging them to register for the news.
"We're going hunting," the message said. "There has been a lot of talk about what Joe Biden is up to, and as one of Joe's best supporters, we want you to be the first to know!"
He jumps into a race that is already underway and will likely be the 20th Democrat to declare his candidacy. He had watched the campaign closely, Aides said after the political debates and the introduction of emerging stars less than half his age.
This is his third run for the White House. But this time, everything is different when he runs as a popular vice president of Barack Obama. It is a far superior position to a Delaware Democratic senator whom he failed in 1988 and 2008.
Biden (76) would be the second oldest candidate of the race with the longest record in the public service. Only Bernie Sanders, 77, is older.
Biden hopes to take command of the high-profile competition with important commitments to highlight how the party's most urgent task should be to defeat President Donald Trump.
But before he can meet Trump, Biden faces a Democratic party that was very different from his last ballot. Progressive issues are more front-and-center than foreign policy, which was a hallmark of his almost four decades in the Senate.
A perennial issue for Biden is his ability to raise funds, especially on the base of the small dollar. Sanders and other candidates have relied on massive online support to generate impressive fundraising numbers.