A group of third-parties, including the Libertarian and Green parties, are suing Texas, alleging that the state’s rules for earning a spot on the ballot are unconstitutionally burdensome.

Plaintiffs in the suit, filed against the Texas Secretary of State in federal district court in Austin, argue that requirements — one of which calls for them to track down thousands of voters who did not cast ballots in a primary election and get their signatures — create a financial barrier to access for their candidates. The suit seeks for a judge to rule the laws unconstitutional and block their enforcement.

“For the last 50 years, the State of Texas has denied voters their right to cast their votes effectively by enforcing a statutory scheme that guarantees ballot access to the two oldest and largest political parties at taxpayer expense,” the suit said, “while imposing ever-greater burdens on their potential competitors.”

Texas’s nomination petition procedure was adopted in 1905 but has not seen much change since, the suit said.

Marc Rylander, a spokesman for Texas Attorney General Ken Paxton, which will represent the state in the suit, did not respond to a request for comment late Thursday.

Rylander told the Austin American-Statesman: “We look forward to successfully defending Texas’ reasonable and longstanding ballot-access measures in court.”

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Among the plaintiffs are Mark Miller, who ran for railroad commissioner as the Libertarian Party of Texas nominee in 2014 and 2016, and Harris County resident Laura Palmer, former co-chair of the Green Party of Texas.

“We filed this lawsuit to restore and protect the right of all Texas voters to cast their votes effectively for the candidates of their choice,” Miller said in a statement. “As plaintiffs, we represent a wide range of political views, but one point on which we all agree is that every citizen has an equal right to participate in Texas’s elections.”

Texas requires third parties to hold a convention with total attendance equal to 1 percent of the votes cast for governor in the last election. If they fail to meet that requirement, they can either spend heavily on the petition drive or pay a filing fee.

Independent candidates are subject to similar provisions.

When the 1 percent requirement first took effect in 1906, it translated to 2,802 signatures for statewide office, the suit said. In 2020, it amounts to a requirement of more than 83,000 signatures.

No independent or third party has met the convention requirement since 1972, according to the suit.

Oliver Hall, attorney for the plaintiffs and executive director of the nonprofit Center for Competitive Democracy, said third parties often have to hire people to circulate petitions at a cost that could easily exceed $600,000 in 2020.

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Texas lawmakers earlier this year passed a bill that allowed parties to have automatic access to the ballot if a candidate received 2 percent of the vote in the last five general elections.

It also added the requirement that candidates either pay a filing fee or submit a petition to appear on a general election ballot — on top of what’s already required for parties.

Hall said such laws limit the amount of viewpoints exposed to Americans, adding that Texas is among the worst states for third-party ballot access in the country. He said other states, such as Arizona, allow petition signatures to be collected electronically and permit candidates more time to collect signatures.

“It’s healthy to have a vibrant, dynamic, open debate where all ideas can be considered,” Hall said. “When you have these restrictions that make it effectively impossible for others to participate and entrench two old established parties, that’s when the system starts to fail and that’s when voters are denied meaningful choices at the polls.”