Humphrey 68=McCain 08?

[Thunderbird is the word]

Both had run for their parties nomination eight years earlier under more favorable circumstances and probably would have won has they got the nomination. Both were at one time seen as men of integrity and widely respected but were shadows of their former selves by the time they got the nomination due to being associated with an unpopular president from Texas and an unpopular war. Both got close to that president (who was from a rival party faction) out of a desperate desire to become president.

[Dr. Cynic]

The difference is Humphrey largely recovered his reputation and he picked a running mate who was an asset to his ticket. McCain did neither.

[Indy Texas]

Humphrey wasn't a counterproductive attention whore in the Senate after his presidential campaign like McCain is.

[Sumner 1868]

Here are a few key differences:

-McCain really never had much chance, while Humphrey closed in at the end.
-Bush had done nothing for McCain to crow about, while Humphrey at least had the Great Society.
-No third party was a major factor in 2008.

[TheElectoralBoobyPrize]

There are some similarities as the OP said, but I think the biggest difference is that while McCain was running in the midst of a financial meltdown, Humphrey had probably the best election-year economy for someone who lost ever, which is partially why it was close. As such, Humphrey didn't bring down the rest of the ticket like McCain did.

[Mechaman]

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.

[SingingAnalyst]

Quibbles: I know of no place in the nation where Humphrey's support was not significantly down from Johnson's, even the deep south where first-time Black voters created the illusion of movement from Goldwater to Humphrey in several Black-majority counties. On the other hand, McCain did significantly better than GWB in several Appalachian and southern, rural, predominantly white counties.