Through good luck or good sense, Democrats have managed to nominate their only top tier 2008 candidate who won’t bring the specter of a sex scandal (either their own or their spouse’s) into The White House. Over the past eight years, former President Bill Clinton’s personal life has been the subject of several press reports that suggest his post-Lewinsky reformation might have been something less than lasting. And now, everyone knows about the mistress and rumored love child that would have derailed John Edwards’ nomination – or presidency.

Certainly, Republicans have suffered their share of scandals over the past couple years. It’s instructive to recall the Democrat reaction to the news, breaking shortly before the 2006 election, that Congressman Mark Foley had sent inappropriate emails to a former congressional page. Immediately, Democrats like Nancy Pelosi and Harry Reid called for an investigation to discover what GOP congressional leaders had known about the matter, and when. Will they now apply the same standards to their own party’s leader?

It isn’t a crime to cheat on one’s cancer-stricken wife. But certainly it is ethically dubious to direct campaign contributions to a slush fund of sorts for one’s mistress – which is exactly what Edwards did, using his political action committee to pay the woman in question $100,000 in a four-month span to create four Web videos of him (ironically, one including a public speech where he discussed morality). The payment was well in excess of market rates, especially given the recipient's lack of relevant experience.

Such an unsavory arrangement should certainly disqualify a politician from running as vice president – or serving as attorney general or accepting a Supreme Court nomination. That is, at least, if the president (or candidate) offering the post is aware of it. Given the mainstream media’s reluctance to cover the Edwards story until it exploded, Barack Obama might well have remained ignorant of it, had he been relying only on media outlets like The New York Times.

But was he? After all, John Edwards was an Obama opponent until he dropped out of the Democratic nominating contest right before Super Tuesday. That means that the Obama campaign must have been conducting opposition research on him. Because rumors about Edwards’ affair – and the allegations about a child resulting from it – were public as early as last December, only a monumentally incompetent opposition research team would have failed to learn of it, or bring it to the campaign’s attention.

Given all this, it’s fair to ask: What did Barack Obama know, and when did he know it? After all, if he was aware of the potential truth of the allegations, it’s revealing of his judgment that he was willing to continue publicly to consider Edwards as a running mate, or for some other high office – and to honor him with a keynote speaking slot at the Democratic National Convention (an offer that’s now been rescinded). Indeed, shouldn’t Obama be asked whether he continues to deem Edwards a viable contender for attorney general or another government post?

It’s far from certain that the mainstream media will, indeed, pose the tough questions to the Democrats’ putative presidential nominee. It’s even less likely that Democrats will seek the same kind of accountability they demanded from Republicans in the wake of the Foley scandal. Obama himself will hardly be eager to raise the subject, given its potential to alienate either the female voters who sympathize with Mrs. Edwards’ plight, or the Democrat partisans who still support her husband. Nevertheless, voters deserve to know where – and whether – Barack Obama draws the line when it comes to behavior like John Edwards’.