http://www.slate.com/articles/news_and_politics/politics/2015/09/scott_walker_drops_out_of_2016_presidential_race_the_wisconsin_governor.html

Scott Walker is the only governor to survive a recall but the first sitting governor who could not survive Donald Trump. The Wisconsin governor dropped out of the 2016 presidential race on Monday, marking one of the fastest flameouts in recent political memory. It was only in July that he announced he was running.* He was at the top of Iowa polls, a climb he had been on since his first strong showing in January at Rep. Steve King’s GOP cattle call.