WASHINGTON — Third party candidates have been trying to get onto the stage at presidential debates for decades, with little success. Since 1988, Ross Perot has been the only one allowed to join a debate, in 1992, and that was only at the request of Bill Clinton and George H. W. Bush's campaigns.

Past attempts to challenge debate participation rules in court have failed. But a coalition of third parties and election reform advocates scored their first major court win on Wednesday evening, when a federal judge in Washington, DC, found that the Federal Election Commission failed to show that it seriously considered the latest round of complaints about the process.

US District Judge Tanya Chutkan described the FEC’s filings in the case as "threadbare." There was no evidence in the record, she wrote, "that the FEC considered the relevant factors or took a hard look at the evidence." She ordered the FEC to go back and explain how it reviewed complaints alleging election law violations by the Commission on Presidential Debates. She also ordered a new review of a challenge to the participation criteria.

The timing of the ruling is significant. Civil lawsuits can last years, especially if there's an appeal. More than three years out from the next presidential debates in 2020, there's time for this case — filed in August 2015 — to play out in court before the next campaign season.

Chutkan's decision "marked the first time the FEC and [Commission on Presidential Debates] have been successfully challenged over debate rules. This is an enormously important ruling. It could pave the way for a new kind of election in 2020," Alexandra Shapiro, a lawyer for the challengers, said in an email to BuzzFeed News.

An FEC spokesperson declined to comment.

Since 2000, the Commission on Presidential Debates, a non-governmental entity, has determined that in order to participate in one of the presidential debates, a candidate must have support from at least 15 percent of voters, according to national polls. FEC regulations require debate "staging organizations" such as the Commission on Presidential Debates to be nonpartisan.

The lawsuit, filed in the US District Court for the District of Columbia in response to the 2012 election, has two parts. The first part involves the FEC's dismissal of two administrative complaints claiming the debate commission and its directors violated election laws by engaging in partisan activity in support of the Democratic and Republican parties. The Green Party, Libertarian Party, and other challengers presented evidence that commission directors contributed to candidates and made statements supporting particular parties.

The second part of the case involves a request by Level the Playing Field — a group that advocates for election reforms — that the FEC revise its rules to block the the commission from using a polling threshold to decide participation in presidential and vice-presidential debates. The FEC declined the request. The challengers presented analysis from experts about the hundreds of millions of dollars a candidate would have to spend to meet the 15 percent polling target, and argued that the rule was not an objective criteria. Instead, they said, it was specifically designed to keep out candidates not affiliated with the Republican or Democratic parties.

Chutkan wrote that the FEC failed to show that it properly considered all of the evidence and arguments presented by the challengers. On the polling threshold issue, she wrote that her "task is made all the more difficult by the fact that the evidence unaddressed — or outright ignored — by the FEC is quite substantial." The judge also said she was "concerned about the agency's cursory treatment" of the rule change petition.

"The FEC appears to have stuck its head in the sand and ignored the evidence that its lack of rulemaking and lack of enforcement may be undermining the stated purpose of its regulations and the [Federal Election Campaign Act]. This is not the reasoned decision-making that is required of all agencies," Chutkan wrote.

A separate lawsuit challenging the presidential debate system is before the US Court of Appeals for the DC Circuit. In that case, third parties and former candidates claimed the debate commission colluded with the Democratic and Republican parties in violation of US antitrust laws. A federal judge in Washington, DC, had dismissed the case in August, but the challengers appealed.