The difference is Humphrey largely recovered his reputation and he picked a running mate who was an asset to his ticket. McCain did neither.
Yes this pretty much. Muskie helped Humphrey compete in and even win states that at the time no Democrat in a close election had no business winning (especially Maine). If the ticket had done just a few points better in a few states (thinking Ohio, Missouri, Illinois, Wisconsin, and then either Alaska, New Jersey, or California) the election would've been theirs. Which I guess is partly why he was seen as a very likely candidate in '72 until the "Canuck Letters" emerged and Nixon basically sidelined the guy by endorsing the creation of the EPA. Palin really didn't do anything to help McCain at all besides making Alaska nearly 60% Republican and making the ticket look like right wing extremists.
No contest.