Rudy Giuliani’s debut as an election lawyer for the Trump campaign is already drawing a high-profile detractor. Former White House Chief of Staff Mick Mulvaney, who called Trump’s attempt to overturn votes in Pennsylvania “the most important lawsuit in the history of the country,” told Fox Business on Wednesday that he was “concerned” by Giuliani’s performance. “There are folks who do this all of the time. This is a specialty,” Mulvaney said. “This is not a television program. This is the real thing.” Giuliani, a former federal prosecutor, last argued a case in federal court in 1992, according to online records. On Tuesday, the 76-year-old former New York City mayor did not appear to understand the legal standard of “scrutiny,” generally struggling to answer U.S. District Judge Matthew Brann’s questions. A final decision in the case is pending.