I was browsing the Cato Institute's website looking at some of the history of the personal account movement, when I noticed this, John McCain in the 2000 primary supported at least some degree of personal accounts
"Like Forbes and Bush, John McCain also supports 'allowing workers to privately invest a portion of the dollars they would otherwise pay the government in payroll taxes.' However, like Bush, McCain has not developed a detailed proposal. In various informal remarks, he has suggested that there should be a national debate on the degree of privatization."
For someone who is considering another Presidential run, who's also a moderate, and would rely on sold support from young people to get elected, it would make sense for Mr. McCain to re-engage on this issue.