Closing Hawaii’s open Democratic primary could all but eliminate competition from other political parties, which would be "bad for democracy," the state warned in a new legal filing in federal appeals court.

The state argues that since Hawaii’s electorate votes heavily Democratic, the winner of the Democratic primary, in many races, will likely take the general election.

The Democratic Party of Hawaii has filed a lawsuit challenging the state’s open primary, which has been in place since 1980, as an unconstitutional violation of the party’s First Amendment right to free association. A U.S. district judge ruled against the Democrats in November, but the party has appealed to the 9th U.S. Circuit Court of Appeals.

Democrats want voters to declare their affiliation before the primary, either by becoming party members or by publicly declaring their support for the party. The state had a closed primary between 1968 and 1978, when voters approved the switch to an open primary, citing privacy and other concerns.

"If voters must formally register with the Democratic Party in order to vote in the election that will effectively decide their representation, the continued viability of the other parties may be threatened," Deirdre Marie-Iha, a deputy attorney general representing Scott Nago, the state’s chief election officer, wrote in a brief to the appeals court.

"Voters will be less likely to support the smaller political parties if this support will necessarily preclude voting in the dominant party’s primary. This is bad for democracy because public policy debates are best conducted when competing viewpoints are tested against each other."

The state has asked the appeals court to uphold the ruling by the district court, which held that Democrats did not prove that the open primary places a "severe burden" on free association rights since other parties might want to welcome all voters regardless of party affiliation. The court also held that the party failed to present evidence of the impact of open primaries on the party’s message.

Democrats have told the appeals court that there is no important difference between Hawaii’s open primary and a California blanket primary that the U.S. Supreme Court ruled was unconstitutional in 2000.

But Marie-Iha said in her brief that there are distinctions. In an open primary, voters privately choose a single party’s ballot in what the state considers an act of affiliation. In a blanket primary, voters can choose candidates from any party as they move down the ballot.

"Voters do affiliate with a political party when they choose to participate in the party’s primary," the state argued. "But the party wants these voters to affiliate in a different way. This is insufficient to show that the burden on the party’s associational rights is ‘severe.’"

The state reserved particular scorn for the party’s argument that it should not have to show evidence of the influence of an open primary on voter behavior. The party has told the appeals court that it would be expensive to compile such voter data and that the party’s rights should not rely "on the fluctuating and irrelevant behavior of others."

Marie-Iha wrote that "the party’s assertion that the open primary is unconstitutional amounts to nothing more than a statement of its own preferences."

The state, as it has from the start of the legal challenge, contended that the open primary removes barriers to voter participation, preserves privacy and protects voters from coercion, and supports a vibrant multiparty system.

Tony Gill, an attorney who filed the lawsuit on the party’s behalf, lost a campaign for party chairman at the Democrats’ state convention last weekend.

Stephanie Ohigashi, the new party chairwoman, said the party would wait and see how the appeals court rules.

"The lawsuit and everything, that’s not my passion," she said. "That was Tony Gill."

Other political parties in Hawaii have refused to join the Democrats’ lawsuit.

The Committee for a Unified Independent Party, an advocacy group for independent voters based in New York, has submitted a friend-of-the-court brief opposing the Democrats’ challenge. The group favors either open primaries or top-two primaries, like the one approved by California voters in 2010, in which the top two finishers regardless of party advance to the general election.

"It is the right to full and meaningful participation in the election of public officials that is at stake in this litigation," the brief claims. "This right, which is recognized by the open primary in Hawaii and other states, is under attack by both the Republican and Democratic parties."