There must be something good about being a purported purist. If grtting rid of two-faced dishonest individuals who lack integrity takes being a “purist”...so be it.
The point is to get what you want, regardless of who gets it for you. If Graham is adopting some conservative positions and will fight for them (even simply in order to get reelected), that’s fine.
What’s done is done, and this means that conservatives have shown enough strength to get him to change his mind or at least his public position. This is a victory, and should be treated as one, regardless of his miserable past track record.
Encourage this now, and make it clear that if he backs down again, your vote is lost. Strangely enough, he’s pretty popular in some parts of SC (my daughter lives there and that’s what she tells me) so if he’s changing his position, that means the conservative influence has got him scared. And it’s a good thing to keep politicians scared....