Ezra Klein wrote brilliantly about this:
The McCain campaign's decision to lie about, well, everything, really needs to be understood as more than the outcome of John McCain's consuming ambition. It is a rational and obvious response to the rules laid down by the media. Indeed, McCain's spokesperson Brian Rogers says this directly to The Politico's Jonathan Martin. "We ran a different kind of campaign and nobody cared about us. They didn’t cover John McCain. So now you’ve got to be forward-leaning in everything."
And it's true. Earlier this year McCain made poverty tours and offered policy speeches. No one cared, Obama retained his lead. It was only when he began offering vicious attacks and daily controversies that he began setting the pace of the coverage. The McCain campaign learned something important about the media: It's an institution that covers conflict. If you want to direct its coverage, give it more conflict than your opponent. And so they have.
None of this, of course, absolves McCain of what he has done. He has sacrificed his honor and dignity with astonishing enthusiasm. He has become much worse than "just another politician." He is a politician who was once more than that, and used that reputation to go lower than the rest. But the fact remains that he wouldn't be doing this, that no one would do this, if the media ignored or censured the behavior. If lies were covered as lies and an allergy to substance was treated as evidence of an unfitness to govern, the tenor of campaigns would lift. These are, at the end of the day, rational beasts, and they hunger for good coverage. The McCain campaign has found its best coverage comes from its worst campaigning. And so they are following the incentive structure laid out by the media.
I don't think it's going to work. There's too much time until the election and the evidence is too obvious.
Here's Andrew Sullivan on the Bridge To Nowhere lies:
Probably much more important is this picture:In her speeches, Sarah Palin routinely and repeatedly uses the phrase: "I told the Congress 'thanks, but no thanks,' for that Bridge to Nowhere." In the McCain-Palin ads, the claim is that she "stopped the Bridge to Nowhere."
These are, again, demonstrable lies. Again I will cite Wikipedia, since it's the fairest summary of the facts of the case, and includes all the links for you to see for yourself:
In 2006, Palin ran for governor on a "build-the-bridge" platform,[101] attacking "spinmeisters"[102] for insulting local residents by calling them "nowhere"[101] and urging speed "while our congressional delegation is in a strong position to assist."[103] About two years after the introduction of the bridge proposals, a month after the bridge received sharp criticism from John McCain,[104] and nine months into Palin's term as governor, Palin canceled the Gravina Bridge, blaming Congress for not providing enough funding.[105] Alaska will not return any of the $442 million to the federal government[106] and is spending a portion of the funding, $25 million, on a Gravina Island road to the place where the bridge would have gone, expressly so that none of the money will have to be returned.[101] Palin continues to support funding Don Young's Way, estimated as more than twice as expensive as the Gravina Bridge would have been.[107]
Your call.

Unfortunately, I think the "lipstick on a pig" lie and the "Obama voted for comprehensive sex ed for kindergartners" lies won't hurt them. McCain can simply stand by the "Lipstick on a pig" lie, as he did on The View, and it's not something one can really prove to be false. The sex ed one won't hurt him, because the refutation doesn't make a good sound bite. Any day talking about "sex ed" and "kindergartners" is a win for McCain.
If he is brought down by his lies, it'll be the lies about Palin. The bridge, the earmarks, and McCain's and Palin's standing by them long after they'd been revealed as lies. The Obama campaign must frame the issue: "Is John McCain a liar?" The contrast between the honorable soldier he presents himself as and the dishonerable campaign he's leading represent a great opportunity for Obama. Rove took Kerry's greatest strength and turned it into his greater weakness, and Obama has the opportunity to return the favor with the message "John McCain is dishonest and dishonerable."