Kansas is one of only four states that make new voters show a birth certificate, passport or other citizenship papers. The Kansas requirement took effect in 2013, and Kobach has directed county election officials to cancel more than 31,000 incomplete registrations, most from people who’ve failed to comply with the requirement.

Here is a look at the proof-of-citizenship law litigation it has prompted:

Incomplete registrations rise

Kobach persuaded the GOP-dominated Legislature to enact the proof-of-citizenship requirements as a way to combat election fraud. Arizona, Alabama and Georgia also have such laws, though they’ve not been fully enforced.

After the citizenship requirement took effect in Kansas, the number of residents with incomplete voter registrations multiplied, reaching nearly 37,700 last week. As of Friday, when Kobach’s cancellation directive took effect, nearly 83 percent had been incomplete for more 90 days.

“It’s a law that has blocked a lot of people from participating,” said Jonathan Brater, an attorney for the voting rights project at the Brennan Center for Justice at New York University’s law school.

But Kobach said anyone whose registration is canceled can submit a new registration form.

“The idea that anyone is being denied the right to vote is patently false,” he said.

The latest lawsuit

Democratic attorneys filed a federal lawsuit Wednesday against the conservative Republican secretary of state over both the proof-of-citizenship requirement and the culling of registration records.

It was filed on behalf of two, young northeast Kansas residents with incomplete registrations. Kobach won the first round when a judge declined to issue an order that would have temporarily blocked the winnowing of records and the proof-of-citizenship law until the case is heard.

The lawsuit alleges Kobach’s efforts violate federal law and voters’ constitutional rights to due legal process.

One of the plaintiffs’ attorneys is former Kansas House Minority Leader Paul Davis, who unsuccessfully ran for governor last year. Both he and Kobach are considered potential candidates in 2018 to replace term-limited Republican Gov. Sam Brownback.

Kobach v. federal registration form

Kobach and Arizona Secretary of State Ken Bennett sued the U.S. Election Assistance Commission in 2013 to attempt to force it to add instructions to the federal voter registration form that Kansas and Arizona registrants must provide proof of citizenship. A federal appeals court ruled against those states in November 2014, and the U.S Supreme Court rejected their appeal in June.

About 200 of the state’s 1.7 million registered voters used the federal form, according to the secretary of state’s office. Kobach declared those who do that are eligible to vote in presidential, U.S. Senate and congressional races but not in state and local elections.

ACLU’S challenge

An American Civil Liberties Union lawsuit filed in November 2013 in Shawnee County District Court says nothing in state law gives Kobach the authority to create a “dual” voter registration system. At that time, he was talking publicly about treating voters who use the federal registration form differently from those using the state form.

District Judge Franklin Theis in August rejected a request from Kobach to decide in his favor without a trial. The ACLU, which is also representing two other northeast Kansas residents, has since asked Theis to rule in its favor, also without a trial; he is not expected to decide until at least December.