LAS VEGAS — A special Saturday night Republican caucus here intended to accommodate Orthodox Jews who could not vote before sundown became the scene of controversy and confrontation after caucusgoers were told that to be admitted they had to sign a legal declaration under penalty of perjury that they could not attend their daytime caucus because of “my religious beliefs.”

Many supporters of Representative Ron Paul of Texas protested when given the declaration to sign. They had arrived at the polling place — a school here named after its benefactors, the casino billionaire Sheldon Adelson and his wife, Miriam — after they received an automated phone call from the Paul campaign saying voters unable to attend their regular caucuses could go to the night meeting.

And Paul campaign aides later said that anyone who had missed their earlier caucuses during the day for any reason should have been allowed to vote, and suggested that what they described as the “religious test” at the caucus would lead to lawsuits.

Mike Dicicco, a Paul supporter who drove 30 minutes from Henderson, Nev., said he was asked whether he was Jewish by a poll worker. Mr. Dicicco said he had received the automated campaign call and could not vote earlier because he had to work, not because of religious reasons.