A law professor from Maryland, Victor Williams, filed as a GOP write-in candidate in New Jersey and other late primary states in order to ensure standing to challenge Cruz’s eligibility. He argues that the Canada-born senator is not a “natural born citizen” as required under the Constitution.

“He’s no different than any of the 650,000 aliens who become American citizen each year — they just didn’t put him through all the hurdles,” he said.

Natural born citizenship is one of the few constitutional requirements to be president. Williams, a law professor at The Catholic University of America, said Saturday by phone that as a candidate who touts himself as a constitutional conservative, Cruz “should know better.”

“He argued many cases before the Supreme Court with a common sense strict construction framework,” Williams said. “It’s just that philosophy, that view point didn’t serve him when it came time to run for president.”

Williams, a Donald Trump supporter, said his primary motivation is to defend that “common sense” interpretation of the Constitution, though he also opposes Cruz as too “extreme.”

“I’m absolutely sure if Donald Trump was born in Canada I would be actively trying to make sure he was not on the ballot,” Williams said. “Even if it were Ronald Reagan, or John F. Kennedy.”

At least five similar challenges have been dismissed by other state election agencies. But Williams argues that his “competitive candidate standing” gives his case more weight than those filed by average voters. Cruz faces four other pending eligibility challenges in state and federal courts. Six others have been dismissed.

Williams filed a challenge with the New Jersey Secretary of State. A hearing is scheduled for Monday morning before the state’s Office of Administrative Law.

Cruz will be campaigning in Southern California on Monday.