Obamacare didn’t just give more people health insurance. It also caused more people to vote.

That’s the conclusion of a new body of evidence that strongly suggests that giving people coverage through expansions of the Medicaid program increases their likelihood of participating in the next election. Medicaid expansions seem to raise both voter registration and voter participation, at least temporarily.

On Tuesday, voters in three states approved measures to further expand Medicaid. The election of Democratic governors in three more could also prompt new expansions. Researchers who worked on three recent studies of the effects say it’s likely that those expansions will have a similar effect on voting in the next election cycle.

“We can confidently say: When you expand Medicaid eligibility, participation goes up,” said Jake Haselswerdt, an assistant professor of political science at the University of Missouri, who wrote one of the papers.

It’s not clear exactly why getting Medicaid makes people more likely to vote, but there are a couple of theories. It could be that Medicaid, which has been shown to increase treatment for depression and improve financial stability, makes it easier for people to participate in the political process by giving them direct benefits. Over all, wealthier and healthier Americans tend to be more likely to vote than their poorer, sicker counterparts.