The ad is a montage of negative ads by the McCain campaign, followed by the closing line, spoken by McCain on his Straight Talk Express in 2000: "If all you run is negative attack ads you don't have much of a vision for the future, or you're not ready to articulate it."
Here's a transcript, h/t to amnesia proletariat:
Quote from Post: "McCain readying aggressive assault on Obama's character"
Montage of McCain attack ads.
"McCain looking to turn the page on economic crisis."
More montage. The parts with Obama's name are cut out. Obamaobamaobamasenatorobamabarackobama
A quote over that from TPM: McCain spending devoted nearly 100 percent to attack ads.
"I'm John McCain and I approve this message."
"...I just have to rely on the good judgement of the voters not to buy into these negative attack ads. Sooner or later, people are going to figure out if all you run is negative attack ads you don’t have much of a vision for the future or you’re not ready to articulate it." - John McCain (Feb 21, 2000)
JOHN MCCAIN: We can't afford more of the same.
And McCain richly deserves the stench of hypocrisy. What else can I say, but this: Here is John McCain, hoisted by his own petard. Thanks, DNC.