The Department of Justice reversed its position in the Supreme Court case over Ohio's practice of purging inactive voters from its rolls, siding with the state in a closely-watched voting rights lawsuit.

In an amicus brief filed Monday, the DOJ solicitor general argued that the state's purge process — in which voters who do not vote over a six-year period, and do not respond to a single piece of mail asking them to confirm their registration two years in, are removed from the voter rolls — is legal under federal law.

The brief, which takes the opposite view of the Justice Department under President Obama, contended that ignoring the notice is a lawful trigger for purge process, and does not amount to a purge due to inactivity.

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“Ohio and several other States have long used a registrant’s failure to vote for a specified period of years as grounds for sending an address-verification notice... That practice does not violate the [National Voting Rights Act],” the new brief said. “Registrants removed using that procedure are not removed “by reason of” their initial failure to vote. They are sent a notice because of that failure, but they are not removed unless they fail to respond and fail to vote for the additional period.”

Career attorneys in the Civil Rights Department, which handles voting rights issues, did not sign this brief, as they did the prior one.

“It’s a signal,” Justin Levitt, the former DOJ deputy assistant attorney general overseeing voting rights cases, told NBC News. “It says this was a political decision that did not have the buy in of the people who are the keel of the Justice Department.”

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“It’s not unheard of for the Solicitor General to change positions, but it’s quite rare,” Levitt added. He said that the solicitor general's office is viewed as the steadiest arm of DOJ, insulated from rapid political shifts by relying heavily on precedent and career attorneys.

“As rare as it is to see normally, it’s really rare to see them switch sides in the same case," he said.

The Sixth Circuit of Appeals ruled last year that Ohio's voter purge process did indeed violate federal law and mandated that purged voters’ provisional ballots be counted in the 2016 presidential election, allowing 7,500 voters’ ballots to count in a critical swing state. The state of Ohio appealed the decision, and the Supreme Court agreed in May to review it this fall.

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The amicus brief is the latest indication of the federal government's about-face on voting rights under President Donald Trump. In February, the DOJ reversed its position on a Texas voter ID law, supporting the law advocates say disenfranchises minorities. In May, the president appointed a voter integrity commission that members have said will seek out proof of fraud, and in June, the DOJ signaled an interest in enforcing federal laws requiring purges as a part of voter roll maintenance with a letter to 44 states asking for details on their purge processes.

Ohio Secretary of State Jon Husted said in a statement that he welcomed the DOJ's support.

“This case is about maintaining the integrity of our elections, something that will be harder to do if elections officials are not be able to properly maintain the voter rolls,” he said.

Vanita Gupta, a signatory of the Obama Justice Department brief, spoke out against the filing.

“Monday’s filing was further confirmation of some of our worst fears about the Trump administration’s crackdown on voting rights," Gupta wrote in a statement on behalf of the Civil and Human Rights Coalition. "Yesterday, the Justice Department abandoned a longstanding view, articulated in a 2010 guidance and through numerous court filings across Democratic and Republican administrations, that the National Voter Registration Act of 1993 prohibits voter purge practices like the one under litigation in Ohio."

Other voting rights advocates also responded quickly to the administration's new position on Ohio's law.

“Since taking office, this Administration has been hellbent on stripping eligible voters of their access to the ballot box," the NAACP Legal Defense Fund said in a statement. "The DOJ’s interpretation of federal law would leave Americans vulnerable to getting purged from the voter rolls, dispossessing millions of a fundamental right simply because they did not exercise it."

The Brennan Center's Myrna Perez called the filing "disappointing and frustrating, but not unexpected." The Center has also filed an amicus brief in the Ohio case.

"I think we are going to see this Department of Justice switching sides on a number of instances," she said. "But the civil rights community is prepared to step into the breach."