 McArdle was first elected to Parliament at the 2004 Queensland State Election, succeeding former Deputy Premier Joan Sheldon.In the 2006 Queensland election, McArdle was returned as the Member for Caloundra, taking a 2.6-point swing in his favour, and increasing his margin to 3.9%.Following electoral redistributions in 2008 prior to the 2009 state election, McArdle's margin was reduced to 1.9%.