Speaking at a Sanders rally in Austin, Texas, Ms Williamson drove home that she sees today’s fight for progressive causes as part of a grand American tradition.
“There were other generations just like this one for whom it was time to take a stand.
“And it was the people in those cases – not the governments, not the elites, not the status quo – it was the people who rose up and the people who woke up and the people who stepped in.
“And now it is our turn.”
Ms Williamson, a left-wing progressive and bestselling spiritual teacher and author, was initially dismissed as a joke candidate when she entered the race, but received a boost after a strong debate performance in July 2019.
However, she soon faced condemnation from her past comments on health and illness – in particular vaccination – and never built up a large following or rose up the polls.
She was never again included in another televised debate, and ultimately suspended her campaign a month before the Iowa caucuses citing a lack of funds.
Ms Williamson’s endorsement comes days after Mr Sanders won the Nevada caucuses with a commanding margin. Having also won the New Hampshire primary and performed strongly in the chaotic Iowa caucuses, he is now recognised as the clear frontrunner in the race for the Democratic nomination.
However, Mr Buttigieg also claimed victory in Iowa. Shortly afterwards, Ms Williamson tweeted: “I haven’t endorsed anyone because there’s more than one good progressive and everyone has to vote their conscience.
“But I submit to my supporters that someone with no real agenda and no real vision for our country beyond a vague notion of inclusion is nothing but a corporate tool.”
Mr Buttigieg went on to narrowly lose the New Hampshire primary to Sanders. His performance in the Nevada caucuses was far weaker: he placed third, behind Mr Sanders and former vice president Joe Biden.