a change in (one's) stripes

A radical, fundamental shift in one's opinion, ideology, or allegiance, especially in relation to politics. Derived from the phrase "a tiger cannot change its stripes," meaning that people are incapable of changing their essential nature. The former president has shown a change in stripes regarding social welfare since leaving office. You're never going to convince Tom about this—he's too stubborn. You'll never see a change in his stripes. Wow, Ben must have had a change in his stripes if he's supporting the more liberal candidate.