After a bruising primary fight, the Republicans will end up nominating Jeb because he'll be seen -- like Mitt Romney in 2012 -- as a moderate who can lose to the Democratic candidate by the smallest margin. And, indeed, in the general election Jeb will lose to Hillary by a small margin. (I'm tired of linking to all the betting and prediction websites that are calling for this. Even CNN has a new one.)
Now, after Hillary beats Jeb by about three or four percentage points (and by even more in the Electoral College), the GOP will go into a four-year introspection about whether or not they would be better off playing to their shrinking base or by trying to expand the party. (Haven't we seen this movie before?) Zzzz...
And, after four more years, if the economy is doing well enough, the Republicans might -- just might -- hit rock bottom and nominate a tea partyer in the mold of Barry Goldwater. (Scott Walker?) Then only after getting positively crushed in 2020 will they begin on the road back to respectability.
Yeah, that sounds about right.