Gov. Mills signed the law last month. “I do believe it is a right that should be protected by law — the right to make ultimate decisions,” she said.

What’s changed?

All these laws require states to track usage and publish statistics. Their reports show that whether a state has six months or 20 years of experience, the proportion of deaths involving aid in dying (also known, to supporters’ distaste, as physician-assisted suicide) remains tiny, a fraction of a percentage point.

California, for example, in 2017 received the mandated state documents for just 632 people who’d made the necessary two verbal requests to a physician, after which 241 doctors wrote prescriptions for 577 patients. More than 269,000 Californians in all died that year.

With such data showing no slippery slope toward widespread use or abuse, “a lot of the hypothetical claims our opponents made no longer carry so much weight with lawmakers,” said Kim Callinan, chief executive of Compassion & Choices.

Ms. Callinan also pointed to changing attitudes within the medical community, once a well funded source of opposition. In recent years, a number of national organizations and a dozen state medical societies have instead adopted neutral stances.

“It levels the playing field a little,” she said.

Opponents, including Catholic organizations and some disability activists, still denounce these laws. In March, an aid-in-dying bill passed the Maryland House of Delegates but failed after a tie vote in the Senate. Opponents are attempting a ballot initiative to repeal Maine’s new law and pursuing a slow-moving court case to invalidate California’s.

Public opinion polls consistently show broad support for aid in dying, however. Compassion & Choices says its upcoming legislative targets include Massachusetts, Maryland again, New Mexico, New York and Nevada.