Progressive activist Ady Barkan, who has amyotrophic lateral sclerosis (ALS), gave a powerful address at the Democratic national convention on Tuesday endorsing Joe Biden for president, calling Donald Trump an “existential threat” and demanding access to quality healthcare for all Americans.

Healthcare is expected to be at the top of voters’ minds ahead of the November election, which has been upended by the coronavirus pandemic that has left more than 170,000 people dead, infected more than 5.4 million people and left millions unemployed, leaving many without health insurance.

“We live in the richest country in history and yet we do not guarantee this most basic human right,” said Barkan. “Everyone living in America should get the healthcare they need regardless of their employment status or ability to pay.”

Barkan is a prominent advocate of Medicare for All, a policy promoted by the Vermont senator Bernie Sanders’s plan to establish a universal health insurance system in the US.

Biden, who was formally nominated as the Democrats’ choice for president during the second night of the convention on Tuesday, campaigned on improving and expanding the Affordable Care Act, or Obamacare, but does not support Medicare for All.

However, as the coronavirus pandemic and its economic fallout continues to devastate communities, Biden has inched left on healthcare.

Nonetheless, Barkan, who has lost his voice because of ALS and has previously testified before Congress using eye movements, urged Americans to vote for Biden in order to avoid the “existential threat of another four years of this president”.

“Even during this terrible crisis, Donald Trump and Republican politicians are trying to take away millions of people’s health insurance,” Barkan said.

“We must elect Joe Biden. Each of us must be a hero for our communities, for our country, and then, with a compassionate and intelligent president, we must act together and put on his desk a bill that guarantees us all the health care we deserve.”

In an interview before his speech aired on Tuesday night, Barkan told the New York Times there was “work to do” to “convince Democratic leadership to shift perspective” on healthcare.

“I support Medicare for All and Joe Biden obviously doesn’t,” he said. “Many Democratic voters agree with me, as evidenced by the overwhelming support in the exit polls during the primaries. And the pandemic and depression have proven how dangerous it is to tie insurance to employment.”

The Democratic convention, which has been radically scaled back and moved almost entirely online, has repeatedly attempted to promote a message of unity between liberals, progressives, moderates and also Republicans.

Barkan was diagnosed with ALS in 2016, at 32 years old. He was little known outside of progressive circles until he cornered the former Arizona senator Jeff Flake on a flight from Phoenix to Washington and urged Flake not to vote for the Republicans’ tax plan. Barkan told Flake about his medical condition and said the tax bill threatened crippling cuts to the federal disability program he relied on for coverage.

Flake ultimately voted for the measure, but the exchange elevated Barkan’s profile. His group, the Center for Popular Democracy, set up the “Be a Hero” campaign to rally Democrats before the midterms. A profile in Politico called Barkan the “most powerful activist in America”.

“I am hopeful about this country’s future because right now, there is a mass movement of people from all over this country, rising up,” he told the Guardian in 2019.

“Nurses, doctors, patients, caregivers, family members – we are all insisting that there is a better way to structure our society, a better way to care for one another, a better way to use our precious time together. If we do the work, we will build the better world our families deserve.”