 On 1 June 2003, Leuenberger was took the place of Patrice Mugny in the Swiss National Council, since the latter had been appointed to the Geneva city executive government.He was re-elected to the National Council on 21 October 2007, following the 2007 Swiss federal election.In 2004, he was appointed Deputy President of the Green Party of Switzerland and in April 2008 he became President, succeeding Ruth Genner.