Wisconsin’s strict voter ID law caused havoc in the state’s primary last week, contributing to long lines at the polls and keeping some voters from casting a ballot at all. But a little-noticed court ruling Tuesday afternoon could go some way toward blunting the law’s impact in November, when the Badger State may be pivotal in the presidential race.

A federal appeals court ruled that a challenge to the ID law as applied to specific voters who face particular burdens to getting an ID can proceed. That means the law’s challengers can now make their case to a district court that voters who are unable to get an ID for certain, specified reasons should be allowed to vote if they sign an affidavit at the polls.

The case will be heard by District Court Judge Lynn Adelman, who in 2014 struck down the ID law, ruling that it violated the Voting Rights Act’s ban on racial discrimination in voting. That decision was reversed by the same appeals court that on Tuesday accepted the challengers’ more limited argument.

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Even if they succeed in the District Court, voting rights advocates say, the ID law will still do real damage as long as it’s in effect, in part because confusion over the law’s rules will cause some number of would-be voters to simply not show up. “Wisconsin’s strict voter ID law remains a threat to our democracy, and will continue to be a threat even if we obtain the remedy that we seek,” said Sean Young of the ACLU, which has led the legal challenge to the law.

But Young said an affidavit option would at least reduce the law’s impact — though by how much would depend on how well it was implemented and publicized. The ID law required the state to conduct a public education campaign informing voters of what they’d need to vote, but lawmakers have failed to approve funds for it.

The ACLU is asking that the affidavit option be created for voters who fall into three specific categories: A voter whose name on her birth certificate doesn’t match her current name, meaning to get identification she would have to go through the time-consuming process of formally amending her birth certificate; a voter who is missing other underlying documents required to get an ID, such as a Social Security card; and a voter whose birth certificate doesn’t exist and can’t be located, meaning she would need to obtain old school records, then hope to get a DMV clerk who chooses to give her an ID (individual clerks have discretion to issue or not issue IDs in such situations). Close video Confusion over Wisconsin voter ID law Ahead of the state’s primary on Tuesday, there are fears that a strict voter ID law could keep many Wisconsinites – especially students and minorities – from the polls. Ahead of the state’s primary on Tuesday, there are fears that a strict voter ID law could keep many Wisconsinites – especially students and minorities – from the polls. share tweet email Embed

The appeals court’s ruling was notable in part because it was issued by Judge Frank Easterbrook, who in 2014 wrote the opinion that rejected the ACLU’s effort to have the law struck down entirely. In that opinion, Easterbrook wrote that the law wasn’t too burdensome, since ID is available to those “willing to scrounge up a birth certificate and stand in line at the office that issues drivers’ licenses.”

In Tuesday’s ruling, Easterbrook wrote that making exceptions for voters who face particular burdens is compatible with that earlier decision. “Plaintiffs’ approach is potentially sound if even a single person eligible to vote is unable to get acceptable photo ID with reasonable effort,” he wrote. “The right to vote is personal and is not defeated by the fact that 99 percent of other people can secure the necessary credentials easily.” Close video Republicans were 'giddy' about voter ID Chris Hayes talks to a former chief of staff for a Republican Wisconsin State Senator who says he was in the room when the voter ID law was conceived. Chris Hayes talks to a former chief of staff for a Republican Wisconsin State Senator who says he was in the room when the voter ID law was conceived. share tweet email Embed

Last week, numerous reports suggested that the law made it significantly harder for some Wisconsinites, especially students and racial minorities, to vote. One of the Republican sponsors of the 2011 ID law acknowledged on election night that it will have the effect of helping Republicans. And a former aide to a GOP state senator told MSNBC that Republican legislators talked openly about how the law would keep students and minorities from the polls.

In addition to its role in the presidential race, Wisconsin also will host a high-profile Senate race, in which Sen. Ron Johnson, a Republican, faces a tough re-election fight against former senator Russ Feingold.