Former Democratic presidential candidate Bernie Sanders has formally endorsed the Colorado ballot measure to create a universal health care system in the state.

At an event in Vermont on Wednesday launching his new political organization, called Our Revolution, Sanders singled out Colorado’s Amendment 69 — also known as ColoradoCare — as something his supporters should rally behind.

“It is absurd, it is beyond belief, that here in America we remain the only major country on earth not to guarantee health care to all people,” Sanders said at the event, according to a news release from the pro-ColoradoCare campaign. “If that proposal can win in Colorado, I believe that idea will spread around the country.”

Sanders became a favorite of progressive Democrats nationwide during his presidential campaign, and his endorsement carries extra weight in Colorado, where he won the party’s caucus this year. His endorsement is not a surprise, though, as he has previously made supportive statements about the ColoradoCare measure.

Proponents of ColoradoCare say they are working to get Sanders to campaign for the measure in Colorado.

“It’s hard to imagine a figure whose support of ColoradoCare is more meaningful than Senator Sanders,” said Owens Perkins, a spokesman for the ColoradoCareYES campaign, in a statement.

Sanders’ endorsement, though, further highlights how the measure has divided Democrats and progressive groups this campaign season. The Colorado Democratic Party’s platform says the party strongly supports ColoradoCare, and the measure has also won the backing of county party branches and the League of Women Voters. But Colorado Gov. John Hickenlooper, U.S. Sen. Michael Bennet and other prominent Democratic figures have come out against the measure, which last week was also opposed by the activist group ProgressNow Colorado.

ColoradoCare would create a universal health care system in Colorado that largely replaces private health insurance and covers all residents. It would be funded mostly through payroll taxes on companies and workers. The system would be overseen by an independently elected board of 21 members, but it would also be considered a political subdivision of the state. People could choose to keep their private insurance, but they would still have to pay the taxes.