Larry Sanders, Mr Sanders’s brother, who lives in the UK and is the health and social care spokesman for the Green Party, voted in Oxford on Tuesday.
Mr Sanders told reporters outside the polling station that he believes his brother is running “on very mainstream policies”.
Fellow Sanders voters chanted and held placards as they joined held placards aloft and chanted as they joined Elizabeth Warren and Mr Bloomberg supporters outside the London voting centre, which was decorated for the occasion with red, white and blue balloons.
Sarah Lansberry, 34, said while she is backing Elizabeth Warren, she trusts that any of the Democratic candidates could beat Mr Trump.
Ms Lansberry, a Seattle native, said: “They’re all polling great against him so I think there’s no qualms there.
“If you’re a Bernie supporter, a Warren supporter, a Biden supporter – they’re all going to smash it.
“I think people are genuinely fed up [of Trump].”
Democrats Abroad UK chairwoman Inge Kjemtrup said she can recall the “pretty much awful” moment she realised Mr Trump had won the presidency in 2016.
“After that, some people wanted to fold in on themselves, but my impulse was to get active immediately afterwards,” she said.
“I’m very hopeful about 2020, I think I kind of have to be. But I also think there’s a very, very strong will [to defeat Trump].”
Ms Kjemtrup added that she is confident Democratic voters will back whichever candidate is nominated.
