Ron Peterson checks signatures on mail in ballots at the voting machine warehouse on November 4, 2008 in Albuquerque, New Mexico.National Journal

New Mexicans are heading to the polls Tuesday to vote in the state's primary elections, but almost a fifth of the state's registered voters are being left out. Nearly 241,000 voters there are ineligble to cast a primary ballot because they have not declared a party affiliation.

New Mexico, like 11 other states, has a closed primary in which only voters registered with a party can vote. Independent and unaffiliated voters are not allowed to participate — even though they are taxed to fund the election, just like their partisan neighbors.

This year, the number of Americans who identify as politically independent reached an all-time high of 42 percent. Since 2008, independents have outnumbered both Republicans and Democrats.

Now, Albuquerque lawyer J. Edward Hollington is bringing a lawsuit against the state to force it to open its polls to all registered voters. The lawsuit argues that closed primaries violate the state constitution, which guarantees voters' rights to cast ballots "at all elections for public officers." Hollington wants the court to allow unaffiliated voters to choose the primary they want to participate in, moving to what's known as a semi-closed model. Semi-closed primaries exist already in a handful of states, including Massachusetts and New Hampshire.

Closed primaries were conceived in the 1970s to prevent crossover voting — that is, to keep Republicans from messing with Democratic primaries, or vice versa. The policy was driven by Democrats, wrote Mark Siegel, who was executive director of the Democratic National Committee at the time these changes were taking place. Closed primaries came about largely in response to the 1972 Michigan Democratic presidential primary, where Republicans crossed over en masse to vote for Alabama Gov. George Wallace, a "racist, unelectable Democrat," according to Siegel.

Writing in 2011, Siegel looked back on the fallout from these changes. He called closed primaries "a significant factor in the polarization of American politics," arguing that the resulting unwavering focus on party politics produced "a Congress of ideologues." He supported moving all states toward the semi-closed system.

At present, primary laws vary widely between states. Thirteen states have completely open primaries and 12, including New Mexico, have completely closed primaries. Two states, Washington and California, have "top-two" primaries, where every candidate's name is listed on the primary ballot (every registered voter gets the same ballot, regardless of party affiliation) and the top two most-voted-for names appear on the general ballot. The remaining states have mixed systems, where political parties are allowed different policies regarding their party's primary elections. Semi-closed primaries fall into this category.

The impending lawsuit against New Mexico's closed primaries is not the first of its kind. In 2011, Idaho Secretary of State Ben Ysursa tried to change his state's closed primary system, but Republicans in the state Legislature shut him down. In Pennsylvania, a bill to open primaries has lay dormant for over a year. And in Oregon, a campaign to put an initiative to open the state's primaries on the November ballot has raised more than $120,000.

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