In front of a large, raucous crowd south of Seattle, the senator said healthcare “was a human right, not a privilege”. For much of his speech, his words were drowned out by the cheers and roars of his supporters.

During debates with other Democrats seeking to become the nominee to take on Donald Trump in November, the Vermont senator has several times asserted his expertise on universal health care by declaring: “I wrote the damn bill.”

In truth he only wrote the Senate version of such a proposal. The legislation introduced in the House of Representatives was written by congresswoman Pramila Jayapal, who has endorsed Mr Sanders and appeared with him in Tacoma on Monday night.

“I’m proud to be the person, along with Bernie Sanders, who sponsored Medicare for All,” said Ms Jayapal, a Democrat who represents Washington’s 7th congressional district, located 40 miles to the north. “[And] tuition for all.”

Democratic candidates compete on the campaign trail: In pictures Show all 18 1 /18 Democratic candidates compete on the campaign trail: In pictures Democratic candidates compete on the campaign trail: In pictures Jessica Canicosa, a precinct captain for Bernie Sanders, waits to greet caucus voters at Liberty High School in Henderson, Nevada REUTERS Democratic candidates compete on the campaign trail: In pictures Hotel workers at the Bellagio in Las Vegas get to grips with voting papers during the Nevada caucuses AFP via Getty Images Democratic candidates compete on the campaign trail: In pictures A caricature of Bernie Sanders is projected on to a tree during a rally in Las Vegas EPA Democratic candidates compete on the campaign trail: In pictures A woman waits to have a photo taken with Elizabeth Warren during a town hall meeting in Las Vegas REUTERS Democratic candidates compete on the campaign trail: In pictures The threat of coronavirus and other germ-borne illnesses was on some voters' minds at the Democratic caucuses in Henderson, Nevada Getty Images Democratic candidates compete on the campaign trail: In pictures Former vice-president Joe Biden takes a selfie with a voter in Las Vegas ahead of the Nevada caucuses REUTERS Democratic candidates compete on the campaign trail: In pictures Amy Klobuchar changes her shoes backstage after giving a speech in Exeter, New Hampshire AFP/Getty Democratic candidates compete on the campaign trail: In pictures A warmly-wrapped-up dog attends an Elizabeth Warren event at Amherst Elementary School in Nashua, New Hampshire AFP/Getty Democratic candidates compete on the campaign trail: In pictures Bernie Sanders, who romped to victory in New Hampshire against Hillary Clinton in 2016, talks to the media in Manchester Getty Democratic candidates compete on the campaign trail: In pictures Joe Biden was hoping to improve on his poor showing in Iowa in the New Hampshire primary Reuters Democratic candidates compete on the campaign trail: In pictures Elizabeth Warren, renowned for giving time to supporters for selfies, works the crowd at the University of New Hampshire in Durham Getty Democratic candidates compete on the campaign trail: In pictures Joe Biden takes a selfie with a supporter and his child outside a campaign event in Somersworth, New Hampshire on 5 February Reuters Democratic candidates compete on the campaign trail: In pictures Elizabeth Warren and Bernie Sanders quarrel after a confrontation in a TV debate in which Sanders claimed that Warren was not telling the truth about a conversation in which she claimed he had said a woman could not win the presidency on 14 January AP Democratic candidates compete on the campaign trail: In pictures Supporter Pat Provencher listens to Pete Buttigieg in Laconia, New Hampshire on 4 February Getty Democratic candidates compete on the campaign trail: In pictures Pete Buttigieg speaks at a campaign event in Concord, New Hampshire while awaiting the results of the Iowa caucus Reuters Democratic candidates compete on the campaign trail: In pictures Elizabeth Warren is presented with a balloon effigy of herself at a campaign event in Nashua, New Hampshire on 5 February Reuters Democratic candidates compete on the campaign trail: In pictures A Trump supporter rides past a rally for Amy Klobuchar in Des Moines, Iowa on 14 January AP Democratic candidates compete on the campaign trail: In pictures A man holds up a sign criticising billionaires in the presidential race in front of Michael Bloomberg in Compton, Califronia. The former New York mayor skipped the first caucus in Iowa and instead campaigned in California on 3 February Reuters

When he took the stage at the Tacoma Dome, where 17,000 people were said to have gathered to see him, Mr Sanders drew attention to many of the issues he has made central to his campaign –​ addressing inequality, combating climate change, working towards criminal justice reform.

He also dedicated considerable time on his vow to pass universal healthcare if he was elected president, an issue that could help propel him into the White House, or derail him if voters consider it too progressive.

No issue has acted more clearly as a marker for the different lanes of the Democratic Party. Elizabeth Warren initially supported Medicare for All, before tweaking her position to allow consumers to stay on a private plan during a three-year transition plan.

Bernie Sanders responds to New Hampshire victory

Pete Buttigieg supports Medicare for those who want it, while Joe Biden would like to see existing coverage –​ remnants of the Affordable Care Act he worked with Barack Obama to pass –​ expanded and improved.

“Healthcare is a human right, not a privilege,” said the 78-year-old democratic socialist. “It is insane we spend twice as much on healthcare per person as Canada and any other [country] on Earth.”

He added: “Despite all of that we have 87 million people, some of them who are here tonight, who are uninsured or under-insured. We have 30,000 people who die every year because they don’t get to a doctor on time.”

Among those who had come to see Mr Sanders were Jessica Livingstone, 36, a nanny from Seattle, who said she had to pay $400 a month for her health insurance. She had supported Mr Sanders four years ago, when she claims the nomination was unfairly denied to him by the Democratic National Committee, elements of which had favoured Hillary Clinton.

“I’ve been a a big Bernie supporter since 2016,” she said. “I think billionaires have too much money.”

Another supporter, Andrea Gamble, 53, an accountant, said she supported many of the senator’s policies. Asked if he could win the nomination and defeat Mr Trump, she said: “I think people will put him over. People are more important than money.”

Mr Sanders’ appearance in Washington state, his first in the 2020 campaign, comes on the back of a virtual tie in Iowa with Mr Buttigieg, and a narrow victory over the former South Bend mayor in New Hampshire.

In Nevada, the next state to vote and which holds its caucus on Saturday, Mr Sanders leads a poll published by Data for Change with 35 points, Ms Warren, 16, Mr Buttigieg on 15, and Mr Biden on 14.