According to Fact Check in an article titled "Scaring Seniors" the "promise" ad says John McCain voted for privatizing social security and quotes him as saying he "campaigned in support of President Bush's proposal."
That is true, as shown by John McCain saying in March of 2008, "I'm totally in favor of personal savings accounts and I think they are an important opportunity for young workers. I campaigned in support of President Bush's proposal and I campaigned with him, and I did town hall meetings with him."
The ad implies that Bush's plan bets the whole lot of Social Security funds on unstable stocks. In fact, it would have "privatized" only a small portion of Social Security taxes that Americans could have invested in private accounts, if they chose to do so.
The "rank misrepresentation" come in when the Obama ad claims it would cut "benefits in half."
Fact check states:
Nobody now getting benefits, or even close to retirement, would have seen any reduction in benefits or cost-of-living adjustments under the plan Bush proposed in April, 2005. What Bush proposed – in addition to creating private Social Security accounts – was to hold down the growth of benefits received by those retiring in the future. He embraced a proposal for "progressive price indexing" of future benefits. This would have been a "cut" only in relation to what the current formula would produce for future retirees, assuming that taxes are increased sufficiently to keep the system going.
The "price indexing" would have tied the growth to the rate of price inflation, rather than to the growth of wages, as is the case now. Wages have historically risen faster than prices, so the current wage-indexed system pushes benefits for future retirees up faster than the rate of inflation. The "progressive" part would have held down the growth only for higher-income and middle-income workers, while allowing benefits for lower-income workers to rise in line with the current wage-based formula.
Fact Check goes on to point out the claims in the new ad attempts to use a report by the Center on Budget and Policy Priorities written by Jason Furman, with Furman now being one of Obama's top economic advisers, then finds the report they are documenting to make their claims actually is "quite different from what the ad claims."
They end their fact checking by saying ads like the Obama-Biden as "misinform" the public and only make the job of fixing the system more difficult.
.