During a contentious Republican debate Rudy Giuliani and Mitt Romney engaged in a heated argument over immigration. Romney accused Giuliani of maintaining New York's status as a "sanctuary city" during his time as mayor. Giuliani in turn accused Romney of employing illegal immigrants and running a "sanctuary mansion," a reference to his opponent having accidentally hired illegal workers as landscapers at his residence. Romney said it would "not be American" to check workers' papers just because they have a funny accent. The two candidates traded more barbs, with Giuliani calling Romney "holier than thou." As the argument escalated further, Giuliani found himself being booed as he persisted in criticizing Romney. Later on Fred Thompson scolded Giuliani for his attacks on Romney. It was not the only time during the evening that Giuliani was booed.