Covered California, the Golden State’s troubled Obamacare exchange, will mail 4 million voter registration cards to residents who have enrolled in health insurance plans (largely Medicaid), the San Francisco Chronicle reports. The state Obamacare exchange was not initially registering voters, but took steps to do so after facing lawsuits from the American Civil Liberties Union (ACLU), the League of Women Voters, and others.

Voter integrity activists have previously raised objections to the use of Obamacare to register voters. The White House has defended the practice on the grounds that the 1993 National Voter Registration Act requires states to offer people the opportunity to register to vote when applying for public services. It is not clear whether the Obamacare exchanges, which are meant to facilitate private insurance transactions, qualify under the law.

As Melissa Clyne of Newsmax noted last year, Democrats stand to gain the most from voter registration through Obamacare, since uninsured Americans supported President Barack Obama by wide margins over Republican Mitt Romney in 2012. In addition, Covered California is known to be targeting minority populations, especially Latino residents of California, as well as young people. Those are both groups that vote strongly Democratic. 

There were 18.1 million registered voters in California as of February 2013, meaning that Obamacare could expand the voter rolls by over 22%, if all enrollees were previously unregistered and chose to register now. However, not all enrollees will be eligible to vote, and many enrollees will likely have registered to vote already, meaning that the actual increase in voter registration, while significant, is likely to be far smaller.