The US Senator Bernie Sanders has dropped out of the race for the Democratic presidential nomination.
It leaves the former vice-president Joe Biden as the party's presumptive candidate for November's general election against Donald Trump.
Vermont Senator Bernie Sanders launched his second campaign for the Democratic nomination last year, and retained large levels of support from young voters and the party's left-wing members following his campaign against Hillary Clinton in 2016.
In a video to supporters today, Mr Sanders - a democratic socialist who has become the most public US proponent of policies such as universal healthcare (Medicare-for-All) - said his grassroots campaigners and contributors had helped change US politics.
He said: "Focusing on that new vision for America has been what our campaign has been about and what we have accomplished.
"It was not long ago that these ideas were considered radical and fringe - today they are mainstream."
Mr Sanders said the path towards victory in the current race was "virtually impossible", and that it was a "very difficult and painful decision" to suspend his campaign.
Despite some calls from supporters to continue campaigning until the final primary votes, Mr Sanders said the ongoing COVID-19 crisis meant he could not in good conscience continue a campaign he could not win.
However, he pledged that the broader movement behind his campaign and policies was not coming to an end.
He said he'd work with Joe Biden to move "progressive ideas forward" and work to defeat Donald Trump in November.
78-year-old Mr Sanders enjoyed some early victories in the primary campaign, picking up crucial wins in New Hampshire and Nevada.
However, Mr Sanders' campaign began to struggle as moderate Democrats such as Amy Klobuchar and Pete Buttigieg ended their own campaigns and threw their support behind Mr Biden.
After a weak start to his campaign, Mr Biden secured key wins in several major states on Super Tuesday and subsequent elector contests - and in recent weeks secured a clear delegate lead over Mr Sanders.
The Democratic field had narrowed to only two candidates over the past month from a field of dozens earlier this year.
Mr Biden and Mr Sanders held their first - and now only - head-to-head debate last month, but no live audience was in attendance due to concerns over the coronavirus.