Ford wins in 1976, and the world is spared Jimmy Carter.
That might kill Reagan (Ford will have the same bad economy Carter did), and it does kill Mondale… in the electoral sense, of course. So the future Presidential contender line-up is quite a bit different.
Ford, actually, might restore a good deal of the public's confidence in the White House. Carter, clearly, was unable to run the government but Ford was. Quiet, though clumsy, competence might just be what the US needs.
As for 1980, it's quite interesting. Carter probably still wins in 1976, and then loses to Ford so he's out. However an open field means you don't need to be a Kennedy to run. Scoop Jackson may give it another try. Daniel Patrick Moynihan could give it a shot. Jerry Brown probably. Kennedy likely is the frontrunner, but isn't guaranteed the nomination by any means.
Republicans, Dole gets the edge because of the VP slot but he sucks at running campaigns. Bush? Reagan? I'm not so sure it matters, because it will probably be as big a Democratic year as it was a Republican year OTL. The Democrats take the Presidency, and strengthen their Congressional majorities. The Republicans don't get their Congressional class of 1980, though 1982 will probably be a good year for them.
That leaves the 1980s entirely different from our '80s, with consequent changes to America.