John McCain has gambled and lost one of the most precious and hard to receive commodities within the political realm. Credibility. Prior to this Presidential Campaign, John McCain, rightfully or wrongfully, had it in spades. So much so that he has taken it for granted and is now shocked and visibly hurt that he it is no longer in his possession.
It also appears that the media pundits are also among the last to recognize that McCain has lost credibility. For them his simple declarative that, "I am not Bush!..." was a winning statement. Completely ignoring the possibility of whether the voting populace actually believed the statement or not.
Late last summer, McCain's campaign and McCain himself decided to use McCain's public perception of being a "straight talker" to tar Obama with numerous false accusations. They gambled that they could make easily demonstratively false statements to cast doubts upon Obama's character believable simply due to McCain's reputation of speaking truth simply by having him repeat it over and over again. When called on the distortion, they would invoke McCain's Credibility and Honor with a "How dare you question McCain's character..." rather than actually give explanation to how they came by such judgments.
At first, the tactic worked. However, just like the "P.O.W." deflections, they overplayed their hand. It became the defacto statement for whenever McCain stretched the truth. The more they used it, the less reserves of credibility were left. Also, since they never actually tried to back up the statements with reasoned proofs and arguments. They never replaced the credibility used, eventually leaving McCain with a significant lack of something he never thought he would run out of.
In the end, this is why the so called "points" that McCain scored in all three debates fell flat. The media pundits assume that all is necessary is to make the statement and everyone will mystically believe it. "Obama will raise your taxes..."; "Obama is going socialize medicine and force you into a health plan you do not want..."; "Obama didn't answer the question..."
What the media pundits ignore is that McCain didn't support his accusations but relied upon his credibility that people would believe them. They ignored that Obama has repeated repudiated and provided concrete examples of how he is not going to raise taxes, that he is not going force people into health plans they do not want and that Obama DID answer the questions, speaking directly to voters.
Such that when McCain stated, "I'm not Bush...", people didn't react the way the pundits did but understand that of course McCain and Bush are two separate people. However, their ideological approach are similar enough to be roughly the same. That McCain no longer has the Credibility to simply declare it and have it believed. That his policies are being compared as he makes the statement and the similarities are too strikingly similar. That trust is no longer a given to McCain. He gambled and lost it to many times over the last few months.