"It's a historic moment for the entire U.S., really," said Kenney Miller, executive director of the Health Equity Alliance.
Tuesday, Mainers passed Medicaid expansion with a 59% majority.
"The voters passed this, so it is the law of the land," said Robyn Merrill of Mainers for Health Care.
In doing so, Maine became the first state where the public, not lawmakers, expanded the program.
"People really do want more affordable health coverage and not less," Merrill said.
The initiative provides coverage to more than 70,000 low income adults, an action supporters say has been a long time coming.
"For us, there are so many people that we work with that have no recourse and no access to health services," Miller said. "It's just going to make such a huge difference in the lives of people struggling with substance use disorders."
"We're going to be able to give them preventative care and keep the costs down instead of having the costs go up or having them show up in the Emergency Room when things have become more critical than they need to," said Lori Dwyer, President and CEO of Penobscot Community Health Care.
Federal funds will cover a majority of the expansion, but legislators will still need to set aside funds from the state budget to cover the rest.
"Hopefully the governor will respect the will of the voters, and hear there is strong support for expanding our Medicaid program to provide more health coverage to people," said Merrill.
Governor Paul LePage has repeatedly blocked Medicaid expansion, and vows to do so again.
Wednesday morning, LePage released a statement saying his administration will not expand Medicaid until it has been fully funded by the legislature without tax increases.