Buchanan and McCain only win like, 5 or less primaries. The main fight for the GOP will be Quayle v Dole. Both are establishment, but other than that, it will kind of be like Clinton v Sanders since that was close.
All of the anti-Gore Democrats will try to associate Gore with the disastrous Clinton campaign, but only win a handful of primaries, mostly on regional lines (Kerry takes some of New England, Gephardt takes some of the Midwest, Bradley only wins New Jersey and Graham only takes Florida) with only Gore achieving nationwide support. I don't know who would win between old, experienced, and uncharismatic but not Gaffe prone (and awesome) Dole vs young, kind of has more experience but gaffe-prone (and also awesome) Quayle. I doubt Bush will endorse any of them before the nominee is decided.
With the General, I can see Dole or Quayle ecking out a narrow victory, but they have to work hard since the American public is suffering party fatigue. If any of the 2 pick Powell, then Buchanan may run 3rd party as he threatened OTL if Dole picked Powell which would had sealed the election for Gore. With Perot, well, I don't think he will make much of a difference.