Even the 2009 incident you're referring to is not really a denial. He is quite careful to neither explicitly endorse it nor deny it. My guess is that he actually is quite on board with evolution, but did not want to alienate a huge chunk of his electorate, who are, in fact, evolution deniers. This segment has been declining in relevance over last decade, hence my comment, that accusing Republicans of being evolution denialists is rather outdated, as that was a Bush-era thing.