He "evolved" - when you live in Washington too long, to be invited to the right parties and schmooze with the famous, you have to compromise your principles. I'm astonished any one remains a conservative for long in that liberal town. Let's put it this way: the Beltway is NOT representative of the country's thinking. To put it in more pithy terms, Danforth succumbed to the disease known as Beltwaytitis.
(Denny Crane: "Sometimes you can only look for answers from God and failing that... and Fox News".)