McCain has been shamelessly pandering to the Talibangelicals, so that makes his adultery and abandonment of his first wife fair game -- the issue being hypocrisy, not (debatable) personal immorality. If he hadn't made "family values" (how I loathe that expression) part of his campaign, I probably wouldn't find his marital history worth fussing over.

(edited to correct a small, but important, typo -- replacing "martial" with "marital" -- although frankly I think his martial history isn't nearly as big of a plus as his supporters tend to make it out to be)