sentences:  Lukes was a frequent critic of Tim Murray during his mayoralty.In 2005, by receiving the second most votes for mayor of anyone also elected as an at-large council member, Lukes became vice-chair of the Worcester City Council by the rules of the city charter.In 2007, after Murray stepped-down as mayor, Lukes became mayor due to the city charter stating that the vice chair would become mayor in the instance of a vacancy.