The last time was Reagan against another Bush. I think Bush is weak enough that it could happen this time. Cruz would be able to expand his support as the debates continue since he isn’t that well-known yet. Bush is so well-known that his support may be close to capped out.
Cruz has some work to do and I don’t think the Fox news debate moderators are going to help him get that work done. And I don’t think Donald is going to “get out of Cruz’s way”.