Orange County Republican leaders on Thursday called for the withdrawal of a GOP congressional candidate they believe sent a letter threatening Hispanic immigrant voters with arrest.

Tan D. Nguyen denied knowing anything about the letter in an interview Thursday with The Associated Press but said he fired a campaign staffer who may have been responsible for it.

County Republican Chairman Scott Baugh, however, said that after speaking with state investigators and the company that distributed the mailer, he believes Nguyen had direct knowledge of the \ufffdobnoxious and reprehensible\ufffd letter. He told the AP that the party\ufffds executive committee voted unanimously to Nguyen to drop out of the race against Democratic U.S. Rep. Loretta Sanchez.