If Humphrey won in 1968

[Mr. Smith]

Would he get re-elected in 1972?

Barring some kind of recession, why wouldn't he? Most of the bragging points Nixon used to win by such a substantial margin were things Humphrey likely would have done, but with more gusto. With enough successes of The Great Society, he might even get chunks of The South [Methinks the set-up Bill Clinton won on sounds about right] back on the same sort of coalition Carter used. (Definitely would if the GOP nominated Rocky)