Oregon Secretary of State Kate Brown signs an “O” for Oregon during a celebration at the Oregon Historical Society to mark the 156th anniversary of Oregon’s admission to the union as the 33rd state in Portland on Feb. 14. (Don Ryan/AP)

Oregon is poised to add an estimated 300,000 voters to its rolls—and potentially hundreds of thousands more in the years to come—in what the state says would be a first-of-its-kind law.

The “new motor voter” bill, which was introduced early last month by then-Secretary of State Kate Brown and cleared its final hurdle on Thursday, requires the state Department of Transportation to share with the Secretary of State information on any resident who provides the proof necessary to register to vote. Those residents would then receive a postcard notifying them that they’ve been automatically registered to vote, with an option to opt out.

“Our goal is to make it as easy as possible for eligible voters to participate in our elections,” Brown, now the governor, said in a statement. “As Secretary of State, the Motor Voter bill was my top priority, and I look forward to signing this bill into law.”

The bill was praised as a model for reform by national groups, such as the Planned Parenthood Action Fund and New York University’s Brennan Center for Justice.

“This legislation is an important paradigm shift on voter registration,” Wendy Weiser, director of the Democracy Program at the Brennan Center, said in a statement. “… This is a bold new standard that other states should work toward as a model for reform.” The nonpartisan Brennan Center, which seeks to “improve the systems of democracy and justice,” was one of several groups that partnered with Brown to pass the bill.

Oregon has already taken steps to expand voting access. Oregon, Washington and Colorado hold elections by mail, with all registered voters receiving ballots weeks before Election Day. As a result, voter turnout in Oregon is among the highest in the country. The new opt-out system would set the state apart even more, making Oregon unique among states for creating such an opt-out system, according to the secretary of state’s office.

“If you go into the DMV and provide proof of age, residency and citizenship, you don’t have to fill out additional information in order to register to vote,” the office’s communication’s director, Tony Green, said in an interview. “It fundamentally flips the default from an opt-in system to an opt-out system.”

Oregon has roughly 2.2 million registered voters, with another 800,000 residents eligible to vote, Green said. An estimated 300,000 residents will be initially and newly registered, thanks to a feature in the bill that allows the state to retroactively register voting-eligible residents who have interacted with the Department of Transportation since 2013.

“Over time we expect to capture almost all of the eligible voters,” Green said.

Brown first proposed the bill two years ago, when it passed the House but died in the state Senate. Sen. Betsy Johnson cast the deciding vote against the measure at that time and was the only Democrat to vote against it this time around, the Oregonian reported. No Republicans voted for the measure.

Democrats generally view the removal of barriers to voting as advantageous, since minority and low-income citizens who often support their candidates tend to be less likely to register. But the bill is expected to swell the ranks of a separate group of voters more than any other, Green says.

It is likely that “there will be more voters affiliated with no party than voters affiliated with any of the major parties,” Green said. Just last month, the state’s independent party achieved major-party status after claiming 5 percent of registered voters.

The bill will cost roughly $750,000 during the 2015 to 2017 biennium and less than $50,000 during the following biennium, according to a Feb. 4 legislative analysis.