Wisconsin state legislator Brett Hulsey, elected as a Democrat in 2010 and re-elected in 2012, is not running for re-election. He says he has left the Democratic Party and is now an independent. He had been elected from Dane County (the county that contains Madison).
He is running as a write-in candidate for Governor. See this story. Also, see this story. He feels that the Democratic nominee for Governor is not all that different from the state’s Republican governor, who is running for re-election.