They should enjoy the party while it lasts because the changing demographics are not exactly in their favor and because they have a habit of alienating just about every key group in politics.
Much is made about the 18-30 crowd growing into voting age and displacing the dead and dying voting base, but we must remember that as millenials age, so do their earnings and investment portolios. Normally this would favor the republicans. However, many of the current republicans, and especially the Trumpsters, are more protectionist and blue collar, and over time the republican party platform may reflect these tendencies. Simultaneously the democrats are appealing less to the rural and the working poor, and more to the very highly educated and upwardly mobile.
Of course the republicans will be in trouble at certain times in the future, and so will the democrats. Still, the two major parties have shifted when necessary to reflect the dominant societal concerns, and I have no reason to think that they would not continue to do so. They take turns being the "in" party. I wish that were not the case--the two major parties are derelict and ideologically inconsistent, winning largely because people do not take seriously alternative parties--but if the past is any guide to the future, then we can assume that the democrats and republicans will continue to be the two major parties by shifting priorities as the voting population changes.
