A federal court clerk entered a default judgment Tuesday against Kansas Secretary of State Kris Kobach for failing to file a timely response to a lawsuit challenging the constitutionality of a state law requiring prospective voters to prove they are U.S. citizens.

It remains unclear whether U.S. District Judge Julie Robinson will give Kobach more time to respond. If the judgment stands it would apply to all voters in all federal, state and local elections — effectively ending the state's proof-of-citizenship requirement.

Kobach did not immediately return a cellphone message, but spokeswoman Desiree Taliaferro said he would comment.

Kobach faces four separate lawsuits challenging various aspects of Kansas' voter registration law. The law, which went into effect in January 2013, requires prospective voters to submit documentary proof of citizenship such as a birth certificate, U.S. passport or naturalization papers.

Kobach, a conservative Republican, has championed the proof-of-citizenship requirement as an anti-fraud measure that keeps non-citizens from voting, including immigrants living in the U.S. illegally. Critics say such requirements suppress voter turnout, particularly among young and minority voters, and that there have been few cases of fraud in the past.

"Oftentimes judges will give an attorney who has not filed something in a timely manner another chance," said Paul Davis, an attorney for the voter who brought the lawsuit. "We will have to see whether Judge Robinson is willing to do that in this case."

Kobach could ask the judge to set aside the clerk's action, possibly on grounds that include "excusable neglect," said Mark Johnson, another attorney for the voter.

But if the clerk's action stands, it means the proof-of-citizenship requirement can't be enforced, Johnson said.

The lawsuit contends the requirement violates voters' constitutional right to right to due legal process and the right to freely travel from state to state by infringing on people's ability to vote and to sign petitions. It also contends the actions Kobach has taken to verify citizenship status discriminates against people who were born or got married in other states.