It's amusing to me to see so many getting physically ill at the thought of Pres Ted Kennedy. Outside of some Obama Derangement Syndrome, I don't think we've seen anything comparable about a recent politician at this forum. With the exception of Chapaquiddick, there's nothing one can point to as an explanation for this reaction, except sheer ideological anger.
Whatever you think of the man, Ted is actually the most accomplished of the three brothers, having a greater effect on the country and doing far more in his time in Congress than, in fact, almost all presidents ever did. Only FDR , Lincoln, and Washington come even close to having the same impact.
The interesting question is how much he could do while president, given his undeniable skills in congressional coalition building. You're talking a congressional leader who staved off much of what Reagan, Gingrinch, and Bush I and II tried to do, at times even when his party was in the minority, and even when the Dems had largely turned their back on their own liberalism for most of the past 40 years. The Dems haven't been a largely liberal party since McGovern ran. TK fought a rearguard action against the GOP often when he had perhaps no more than 1/3 of his party to back him.
So if Ted Kennedy was pres in 1980, think of the following as quite likely:
No Iran Contra. No Contras period. The Sandinista Revolution gets to try out their experiment without having to fight off the world's most powerful nation. (This deserves its own thread.)
Death squads in Ctrl America have to pay their own way. That means likely an earlier return to democracy in El Salvador, and a Guatemalan junta that has no outside support except Israel and other Latin American dictatorships.
A US pres who sees Gorbachev as a reformer from day one. (Assuming TK's reelection.) In fact TK would likely try to negotiate with Andropov and even Brezhnev. Potentially this means the USSR may survive since reforms come earlier.
No Savings and Loans scandal, unless TK is defeated for reelection. The decade of greed dies stillborn, or at least its worst practitioners have to face the music sooner.
Ironically, TK will be far more fiscally conservative than Reagan was. Far less of a largely useless military buildup that includes ridiculous items like bringing back battleships. American debt is at least 1/4 less today.