On Saturday, California governor Jerry Brown signed a bill that will start automatically registering adult citizens to vote. Starting in 2016, every adult citizen in the state who gets a driver's license, renews a license, gets a state identification card, or fills out a change of address form with the Department of Motor Vehicles will be registered to vote — unless he or she declines to be registered. Earlier this year, Oregon became the first state in the country to automatically register voters. California is now the second. (North Dakota is the only US state with no voter registration system at all.) Democrats in California's legislature overwhelmingly supported the bill, but Republicans overwhelmingly opposed it, with several citing concerns about potential voter fraud. About one-fifth of the state's 38 million people are eligible to vote, but not registered, according to the Los Angeles Times's Patrick McGreevy.

Why automatic registration is such a big deal

Federal laws already allow people across the country the option to register to vote at the DMV. But Oregon and California's laws are pioneering because they do it automatically.

It's hard to overstate how novel this concept is for the US. Throughout much of United States history, governments frequently put up barriers aimed at preventing people from voting, such as property ownership requirements, poll taxes, or literacy tests.

Gradually, many of these barriers have fallen to make it easier for people to register. However, many states, including California, still close off registration weeks to a month before an election — an artificial obstacle that can prevent perfectly qualified people from voting if they simply miss a deadline.

These new proposals remove those obstacles. Oregon's law will register all adult citizens in the DMV's database, while California's law will be implemented more gradually, as people get or renew their licenses or state IDs, or change their addresses. But both make it the government's responsibility to ensure that all eligible voters are registered.

So it's a big deal that governments are now trying to make it easier and easier to vote, rather than more difficult. Matt Yglesias has argued for going even further and enshrining an affirmative right to vote in our Constitution — read his case here.

Support and opposition have been breaking down along party lines

In both California and Oregon, Republicans opposed these proposals, but generally didn't argue against the principle of easing registration. Instead, the criticisms have fallen along two main lines.

First, critics have argued that since voter registration data is more publicly accessible than DMV information, automatically adding voters to the rolls could pose privacy concerns. However, supporters respond that people can always opt out.

Second, some Republicans have cited concerns about voter fraud — usually about potential registration of unauthorized immigrants. But while California began issuing driver's licenses to unauthorized immigrants this year, these licenses are distinctively marked, and people with them would not be registered to vote automatically. And Oregon requires proof of citizenship for all driver's license applicants.

Meanwhile, national Democrats are increasingly adopting mandatory voter registration as a major cause. In a speech on voting rights this June, Hillary Clinton called on all states to automatically register citizens to vote when they turn 18, unless they choose to opt out. And legislators in 15 other states have introduced bills similar to Oregon's new law — the Brennan Center is tracking them here.