by Alice Ollstein THINK PROGRESS

CREDIT: AP Photo/Troy Wayrynen

Naomi Scott, center, of McMinnville, Oregon, takes a picture with Democratic presidential candidate Sen. Bernie Sanders.

For decades, Oregon has been at the forefront of making it easier to vote. Two decades ago, the state began offering each and every eligible resident the option to vote by mail. Oregon later became the first to conduct all its elections by mail. Then, in 2015, Oregon became the first state in the nation to automatically register voters every time they visit a Department of Motor Vehicles.

The new “Motor Voter” policy has added more than 67,000 new voters to the state’s voter rolls, and officials are hoping Tuesday’s primary will have record turnout. The new system has especially been a boon for young voters; since September, the number of registered voters between the ages of 18 and 29 has increased 21 percent.

Yet thousands of voters who received ballots in the mail over the past few weeks may have been surprised to learn they can’t cast a vote in the presidential primaries. Oregon operates closed primaries, meaning that only registered Democrats can decide between Bernie Sanders and Hillary Clinton, and only registered Republicans can decide between Donald Trump and the ghosts of Ted Cruz and John Kasich, who have already bowed out of the race. Under the new DMV system, voters are automatically registered as “unaffiliated,” and later receive a form in the mail giving them the option to change their party affiliation or opt out entirely. The vast majority — 76 percent — did not take that extra step by the late April deadline, and thus can’t participate in the presidential primary. They will still be able to vote in some local races.

Oregon Secretary of State Jeanne Atkins admitted to the Associated Press that the system is not “the way we’re going to get the most participation.” She added that she and other Oregon officials are exploring whether DMVs can collect additional data and sign people up for the party of their choice automatically, as California plans to start doing next year.

Tuesday’s closed primary is expected to once again hurt Sanders, whose appeal to Independent voters has been a major strength of his campaign, and who has repeatedly lost to Clinton in states where only registered Democrats can cast a ballot. The exclusion of Independents caused an uproar and a lawsuit in New York, and was a contributing factor to Arizona’s primary day chaos. Clinton won both states.

Sen. Jeff Merkley (D-OR), the sole sitting member of the Senate to endorse Sanders, told CNN on Monday: “A lot of the Independents who have been coming out to the Bernie rallies aren’t going to be able to vote. That’s unfortunate.”

To combat this disadvantage, the Sanders campaign worked for months to find and register supporters as Democrats before the April 26 deadline, targeting college campuses, farmers’ markets, and other places where young progressives were likely to congregate.

The campaign’s effort, combined with the state sending out mailers reminding residents of the deadline to switch parties, may have paid off. The Oregon Democratic Party saw registration climb by 16 percent between September 2015 and April, while Republican registration grew 7 percent during that time. Democrats now make up 42 percent of Oregon’s electorate — an increase of four percent from 2015 — while the GOP’s share of the electorate has stayed flat.

A proposal to create an open primary went before Oregon voters in 2014, and was rejected by two-thirds of voters.