The new law provides for a significant expansion of so-called conditional voter registration, which allows a new voter to cast a ballot that is counted after eligibility is determined during the 30-day vote-counting period after an election. That process began in last year's statewide election, but registration was only available in county elections offices. Starting next year, voters can register on Election Day anywhere ballots are cast.

Sixteen states, along with the District of Columbia, already allow Election Day voter registration. Supporters have argued the laws boost turnout, as some voters become energized by political campaigns only after registration deadlines have passed. Prior to Newsom signing the new law, California's voter registration deadline was 15 days before Election Day.

California voting rights advocates have been pushing for what's broadly known as "same-day registration" for years. Lawmakers gave approval to the first phase of the program in 2012, but made it contingent on the completion of a new statewide voter registration database - which was certified in 2016, more than a decade overdue. Elections officials reported about 57,000 Californians used the last-minute registration process in 2018 - a relatively modest amount that could be attributed to the fact that most counties only offered same-day registration at just one elections office.

The new law will change that. In counties with neighborhood polling places, voters will be given a ballot for their precinct or - in the event that's not possible - told that their vote will be counted only in races for which they are eligible.

Fifteen counties, including Los Angeles, will conduct next year's election under a 2016 law that uses a limited number of multipurpose "vote centers" instead of polling places. In those counties, new voters should be able to have ballots printed that match the precinct in which they are registered.

The option to register on Election Day also provides another service: It allows a voter to change party preference at the last minute. That could alleviate the complaints lodged by some voters in 2016 who thought they were unaffiliated independent voters and thus eligible to vote in the Democratic Party's presidential primary.

Those voters, in fact, mistakenly registered with the American Independent Party, confusion documented in a 2016 Los Angeles Times investigation. Democratic Party rules stated AIP voters could not request a ballot in that year's race between Democrats Hillary Clinton and Bernie Sanders. Under the law signed on Tuesday, any voter can re-register on Election Day.

As many as 6 million Californians are eligible to vote but not registered. Advocates believe the new law could significantly reduce that number, particularly as more people realize they can make the decision at the last minute.