All of the above points are reasonable. I would focus on the lack of a coherent, positive message, the vast difference in financial resources, and the economic meltdown, which McCain, for some reason, was unwilling to pin on the Democrats trying to promote well-meaning but misguided social policies.
There is also one other thing that wasn’t mentioned above.
Barry Goldwater recounted that he and JFK, who were friends from the Senate, had agreed that if they ran against each other, they would go around together and debate the issues all over the country. After JFK was killed, it is reported that Goldwater didn’t really want to run against Johnson. His heart wasn’t really in it. And, quite possibly, he didn’t adapt his election strategy accordingly, though it is not clear that he could have won under any circumstance given the situation in the country that year.
I can’t prove this, but my impression is that there was something similar going on with McCain. I think he had planned and expected to run against Hillary, who he was friends with from the Senate. After all, it was a foregone conclusion for a long time that Hillary would be nominated. I think McCain expected to run a civilized campaign that was focused on issues with little or no negative campaigning (Hillary’s negatives were long known). I think that when Obama was nominated, McCain tried run against him as if he was Hillary, and only rather late in the game started to adapt his strategy.
