http://www.newsweek.com/id/159875
An Obama-Biden ad says McCain supports "cutting benefits in half" for Social Security recipients. False!
Summary
A new Obama ad characterizes the "Bush-McCain privatization plan" as "cutting Social Security Benefits in half." This is a falsehood sure to frighten seniors who rely on their Social Security checks. In truth, McCain does not propose to cut those checks at all.
The ad refers to a Bush proposal from 2005 to hold down the growth of benefits for future retirees. Compared to the buying power of benefits paid to today's retirees, that would not have been a "cut" for anybody. It would have been a "cut" of half only in relation to benefits now promised to retirees who have yet to be born. And for average workers, that "cut" in 2075 was projected by one of Obama's own economic advisers to be 28 percent, not "half."
The ad also says McCain voted "in favor of privatizing Social Security." The term "privatizing" could give the wrong impression. McCain does support creating government-managed accounts that would allow individuals to invest some portion of their Social Security payroll taxes in widely diversified stock or bond funds.

Re: Fact Check: Obama-Biden "scaring seniors"
It's obnoxious, but unfortunately this type of campaigning is happening on both sides of the aisle.
The ad is clearly not running here. But since it's running in your home state, I'd recommend sending a letter to the editor of local newspapers. That's where I often learned the different sides of arguments.