On February 17, Indianapolis city councilmember Edward Coleman publicly announced that he had left the Republican Party and joined the Libertarian Party. Indianapolis, which has a city-county merged government (Marion County-Indianapolis), has partisan elections. Coleman is one of the 4 at-large members and was last elected in November 2007. He must run for re-election in November 2011.
Indiana does not have registration by party. Therefore, there is no piece of paper that makes Coleman’s switch “official” other than his becoming a dues-paying member of the Libertarian Party, and of course his declaration of candidacy if he runs for re-election in 2011. See this Chicago Tribune story about Coleman’s party switch.