California is bucking a national trend this election season, making it easier for people to vote while many states are making it harder.

Those forms you may remember picking up from the library or post office are no longer necessary to register to vote. With a few mouse clicks, Californians can now register or update their registration.

Because of a law Gov. Jerry Brown signed last month, state residents also should be able to register to vote as late as Election Day by the next presidential election in 2016.

Over time, experts believe, the changes will add many new voters to the rolls – especially those who are young or non-white, groups less likely to register now.

Compare that with other parts of the country, where lawmakers are reducing registration opportunities or establishing new requirements that voters show photo identification at the polls.

The reason for the difference can be explained largely by politics.

States passing voter ID laws tend to be controlled by Republicans. They argue the need to thwart voter fraud, but also tend to benefit from a smaller, more conservative electorate.

Democrats, in charge in California, argue that the electoral process needs to be accessible to more people – a dynamic that helps their candidates' chances. Young people are driving California's population shift toward more diversity.

"If you bring in younger voters, you bring in ethnic voters, and they're more likely in California and probably in other states to vote for Democrats," said Mark DiCamillo, director of the Field Poll that tracks voter demographics. "So expanding the voter rolls will help Obama and the Democrats."

Kim Alexander, president of the nonpartisan California Voter Foundation, said the "political stars aligned" to expand voter access in California with the election of a Democratic governor in addition to the Democratic legislative majorities and secretary of state.

"That's not the case in many other states," she said.

In the last two years, the number of states requiring voters to show photo ID has grown from two to eight, according to the Brennan Center for Justice at New York University, though courts blocked the photo ID law in Pennsylvania, Texas and Wisconsin, and are reviewing it in South Carolina.

Three states – Alabama, Kansas and Tennessee – passed laws requiring voters to show proof of citizenship to register, the center says. At least 16 states introduced bills to make registration harder by limiting registration drives, changing registration procedures when people move, or repealing the very things California recently approved – same-day and online registration.

"Each political party has its own preferences about which voters should be able to vote more easily than others," said Nate Persily, a law professor at Columbia University who focuses on voting and election law.

"So the rules the different parties propose are biased in favor of some voters over others."

Mike Turzai, a Republican legislator in Pennsylvania, illustrated that point when he said this summer that the state's voter ID law "is going to allow Gov. Romney to win the state of Pennsylvania."

A super PAC supporting President Barack Obama's re-election seized on the comment, producing a YouTube video with liberal comedian Sarah Silverman railing against voter ID laws. In it, she says they're "presented as a way to prevent voter fraud but are in fact designed to make it hard for specific people to vote: black people, elderly people, poor people and students."