Bernie Sanders has endorsed Hillary Clinton as the Democratic nominee in the race for the White House.
The Vermont senator stood side-by-side with his former rival as he backed Clinton at a rally in Portsmouth, New Hampshire - where Sanders defeated Clinton by a wide margin in the nation's first primary.
He pledged that his "political revolution" would continue, but acknowledged that Clinton had won the delegates required to snag the nomination.
This has been true for weeks and Democrats have been angling for self-described democratic socialist Sanders to drop out of the campaign and endorse the former secretary of state.
Sanders promised to work to help Clinton win in November, calling her "far and away the best candidate" to confront the challenges facing America.
He called for unity and vowed to do everything he can to help her beat Donald Trump.
Listing his reasons for the endorsement, Sanders said: "Hillary Clinton understands that we must fix an economy in America that is rigged and that sends almost all new wealth and income to the top 1%.
"Hillary Clinton understands that if someone in America works 40 hours a week, that person should not be living in poverty."
Sanders saw his long-shot bid for the White House quickly catch fire in 2015 at large-scale rallies where he denounced income inequality, the influence of Wall Street and the role of big money in politics - all part of a system he described as "rigged".
His endorsement could help bring some of his supporters - mainly college students, independents and white voters drawn to his anti-establishment message - into the fold for Clinton as she prepares to face off with Trump in the autumn.
Trump - who previously said Sanders had been "treated terribly by the Democrats" and should have run as an independent - wasted no time in going after the Vermont senator on Twitter.
His campaign said Sanders "is now officially part of a rigged system".
Senior policy adviser Stephen Miller said the Vermont senator is "endorsing one of the most pro-war, pro-Wall Street, and pro-off-shoring candidates in the history of the Democratic Party.
"The candidate who ran against special interests is endorsing the candidate who embodies special interests."