I should also point out I think it will be very chaotic if the infighting in the House of Saud starts while Obama is still in power. Perhaps it's bias, but I don't think he has a game plan to take advantage of events to edge towards an outcome most beneficial to the US. No one could guarantee one, of course.
How much influence do you think ANY US president would have in an internal struggle among the Al Sauds and the internal religious institutions? Do you honestly think that we'll really have any significant say in the end there regardless of who is in office? Our public backing of any individual candidate in Saudi Arabia is more likely to hurt them domestically than help them. In order to come out on top, any Prince in likely going to need to court the religious institutions and being a friend of the US isn't likely to help with that.
This is an interesting response, and telling in a way.
You're asking me how much "say" the US will have. The answer if Obama is president is virtually none, because I doubt he has any plans. However, like or hate him, Bush would have had plans. And they would be based on the interests of the current leaders, simply because he did have a relationship there. Is that a guarantee of anything? Of course not. But he would have had an opportunity. Which is about all you can have, non militarily.
Now I'm confident we both know that a direct endorsement of any candidate would backfire. But that is the same in any country. If Israel directly endorsed any candidate, it would probably destroy their chances. If any other country did, it would have the same result. That's elementary and pointless to even mention, so I'm surprised you mentioned it. I find it telling in the sense that the likely reason you did is that you believe Obama to be unprepared for it also.