Repeal the 17th Amendment. This is not rocket scence.
Ummmm... yeah... right...
Okay, so, let me try to follow this -- IF we let local state party hacks pick our U.S. Senators FOR us (God knows they did such a great job with Lisa Murcowski, John Barrasso, Frank Lautenberg, John Warner, eh?), somehow, in your convoluted thought process, this will lead to us picking better Presidential candidates in the completely unrelated topic of presidential primary races.
I dunno what you've been smoking, but it's definitely not legal.
Or perhaps you're really warped and you'd like to see our President appointed FOR us as well. Can't let the little people have any say in who their candidate is. Miss the good ol' days of Jerry Ford, eh?