In the 2003 and 2006 elections, Cullen faced strong challenges from conservative opponents. In the 2003 election he faced John Blatherwick, while in 2006 he fended off a challenge from high-profile former mayoral candidate Terry Kilrea.
In the 2003 and 2006 elections, Cullen faced formidable opposition from conservative challengers. In 2003, his primary opponent was John Blatherwick, whereas in 2006 he defeated Terry Kilrea's challenge, who had been a notable mayoral candidate.