Both the incumbent Howard Coalition government and the Rudd Labor opposition promised to implement an emissions trading scheme (ETS) before the 2007 federal election. Labor won the election, with the new government proceeding to implement an ETS. The government introduced the Carbon Pollution Reduction Scheme, which the Liberals supported with Malcolm Turnbull as leader. Tony Abbott questioned an ETS, saying the best way to reduce emissions is with a "simple tax". Shortly before the carbon vote, Abbott defeated Turnbull in a leadership challenge, and from there on the Liberals opposed the ETS. This left the government unable to secure passage of the bill and it was subsequently withdrawn.