It's always worth taking a break from vacation to behold the spectacle of a politician blowing off his own foot.

John McCain this week has uttered a couple whoppers that are so egregious, it prompts one to wonder whether he is subconsciously trying to sabotage his own campaign, or whether he is as verbally inept as the president he seeks to replace, or whether he simply lacks the most fundamental knowledge that is required of any Oval Office denizen.

The topic was Social Security. During a Monday town hall event (and bear in mind that he thinks he excels best in town hall events), the presumptive Republican nominee stated: "Americans have got to understand that we are paying present-day retirees with the taxes paid by young workers in America today. And that's a disgrace. It's an absolute disgrace..."

One day later, on CNN, McCain said virtually the thing while railing against the Social Security program: "Let's describe it for what it is. (Today's workers) pay their taxes, and right now their taxes are going to pay the retirement of present-day retirees. That's why it's broken..."

We all know that McCain would prefer to spend his time talking about national security and about how Iraq is the central front in the war on terror. We're all aware by now of his public admission that he is a tad knowledge-challenged about the biggest domestic issue of all, the economy. But we might arguably expect that the presidential nominee of a major party would at least have a working knowledge of the most popular domestic program since the New Deal.

Because here's the thing: What McCain describes as "an absolute disgrace" and "broken" are the rules that have governed the Social Security program since its inception 73 years ago. Current workers are always taxed, via the payroll levy, to support the retirement security of current seniors. That's how the pay-as-you-go policy has always worked. That's not a "disgrace," that's the law.

There are several possible ways to interpret McCain's remarks, none of them very flattering:

1. He's truly ignorant of how Social Security works, which, among other things, is not the best way to attract senior voters, or any voters who'd like to believe that a guy auditioning to run the country is at least minimally in touch with reality.

2. He does know how Social Security works (it's hard to imagine he doesn't, not after two decades in Washington), but somehow failed to articulate whatever he really intended to say - just as he has done on other recent occasions, such as when he twice confused the Sunnis and the Shiites (which Brit Hume of Fox News defended as a possible "senior moment").

3. He actually does believe that the fundamental precepts of Social Security are an "absolute disgrace," and wants to overhaul them.

It has long been an axiom that any Republican seeking to overhaul Social Security is doomed to suffer political damage; witness President Bush, who drained his '05 capital while stumping in vain for partial privatization. And it has long been an axiom that any Republican who verbally disses the program (inadvertently or intentionally) is doomed to suffer political damage; witness Barry Goldwater, the 1964 presidential nominee who was slaughtered on election day in part because he was on record as having stated, "I think Social Security ought to be voluntary. This is the only definite position I have on it."

Yesterday, a McCain spokesman tried to cover the candidate's tracks (they've been mopping up a lot lately) by stating after the fact what McCain might have been intending to convey: "The disgrace is our failure to fix the long-run imbalance in Social Security - a failure of leadership evidenced by our willingness to kick the problem to the next generation of leaders. He's also describing the looming and increasing demographic pressures confronting the Social Security system and Washington's utter failure to address it."

But that's not what McCain described as a "disgrace." Instead, he targeted the underlying premise of the program itself. Either he did this because he is inarticulate; or because he really doesn't know how it works; or because he's an idealogue who wants to undo the best of the New Deal. Whatever the reason, the Demcrats and the senior groups now have him on video. As Barry Goldwater discovered, while trying unsuccessfully to distance himself from his own words, that kind of talk can kill a presidential candidacy.