The presidential campaigns’ recent detour to the dirty side has pundits decrying the strategy as manipulative and irrelevant, and urging the candidates to return to the issues. But negativity isn’t all bad.

The ostensible point of a two-year-long presidential campaign is to give voters enough time to discover how each candidate would govern. And issues-based campaigning only goes so far. Presidencies aren’t built on plans so much as on reactions; Barack Obama said as much in last night’s debate. George W. Bush enunciated plenty of policies in the course of the 2000 presidential campaign, but his presidency was defined by his reaction to the events of September 11, 2001. And reactions and judgment are arguably shaped by character as much as by ideology.

So it’s entirely valid for John McCain to make the next month “a referendum on character,” as Adam Nagourney wrote in yesterday’s New York Times, and his readiness to do so implies that he thinks pretty highly of his own character. But should he?

In the current issue of Rolling Stone, Tim Dickinson has a story entitled “Make-Believe Maverick” that depicts McCain as a spoiled, bullying opportunist who milked family connections to advance his career and serially mistreated the women in his life. Dickinson writes that “pandering to the right is consistent with the only constant in his life: doing what’s best for himself. To put the matter squarely: John McCain is his own special interest.”

These general points have been raised (and ignored) before. But Dickinson also raises several questions that strike at McCain’s near-mythic record of military heroism. He dings McCain for remaining below decks after the inadvertent bombing of the U.S.S. Forrestal, for providing military information to the North Vietnamese while other P.O.W.s remained silent, and for exaggerating the number of years during which he was actively tortured. And he insinuates that McCain may have embellished his own anecdotal accounts of his incarceration.

Ancient history? Sure. But this is a presidential campaign. Everything is fair game. If we’re going to speculate about irrelevancies like Sarah Palin purportedly covering up her daughter’s illicit pregnancy, or Barack Obama’s ties to Bill Ayers, then we can certainly speculate about the veracity of the events that constitute the mythos on which John McCain has built his political career. And perhaps we should.

Rolling Stone’s allegations don’t say very much about McCain’s policy proposals. But they say a lot about McCain’s character, and if we want to gauge the way a potential President will react to crises, character matters very much. Here’s what Colin Powell’s chief of staff says in Dickinson’s article: “I’m not sure that much time in a prisoner-of-war status doesn’t do something to you. Doesn’t do something to you psychologically, doesn’t do something to you that might make you a little more volatile, a little less apt to listen to reason, a little more inclined to be volcanic in your temperament.” Certainly these are issues at least as relevant and compelling as those raised by the spectre of Barack Obama’s acquaintance with a long-reformed (if largely unrepentant) student radical.

If John McCain is going to tether his campaign to character issues, he should be ready and willing to face questions about his own. If the media is going to let him dish it out, then they ought to force him to take it.

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Justin Peters is editor-at-large of the Columbia Journalism Review.