I have a question about reports that former Sen. John Edwards (D-N.C.) could face criminal charges relating to his extramarital affair with a campaign worker. I have a hard time understanding this. I certainly think that what Edwards did was awful, particularly given that his wife was battling cancer at the time. But as reprehensible as it is to have an extramarital affair, it seems odd to me that it would be illegal, even for a politician. Is it a crime for politicians to commit adultery?

It’s not the affair. It’s the cover-up. Isn’t it always?

Well, perhaps not always. But you do not have to look far to find a recent example of a politician in legal hot water for conduct following an extramarital affair. Former Sen. John Ensign (R-Nev.) resigned last month amid a Senate Ethics Committee investigation of his conduct relating to an affair with a former campaign worker. According to the committee’s report regarding the investigation, the conduct that could expose Ensign to liability is not the affair itself, but rather what he did after the affair.

In particular, the report states that Ensign may have violated campaign finance laws for his involvement in a $96,000 payment from Ensign’s parents to his former mistress and her family. Ensign and his parents have said the money was a gift. The Ethics report concluded, however, that the money may have been, in part, a severance payment to Ensign’s mistress upon leaving Ensign’s campaign. This is significant because if it were a severance payment, it technically would have come from Ensign’s campaign and therefore would have qualified as a contribution from Ensign’s parents to the campaign in an amount that well exceeds the annual contribution limit. The report also cites other examples of possible illegal conduct by Ensign in seeking to minimize the damage stemming from his affair.

In Edwards’ case, few people would dispute that his conduct was wrong. Edwards has admitted to fathering a child with a former campaign worker while his wife battled metastatic breast cancer, a disease that would eventually result in her death. In 2010, one polling organization, Public Policy Polling, called Edwards “the record holder for the most unpopular person we’ve polled anywhere at any time.”

But there is a difference between being unpopular and being a criminal. And Edwards, like Ensign, is being investigated not for his adultery itself, but for conduct surrounding his affair. While the nature of the charges Edwards might face remains unclear, reports suggest that the focus of the investigation could be possible misuse of campaign funds. A former Edwards staffer claims that friends of Edwards gave hundreds of thousands of dollars to help cover up his affair. At issue may be whether any of this money should have been treated as a campaign contribution. There are reports that Edwards could face an indictment as soon as next week and may be considering a plea deal.

The fact that the Edwards and Ensign investigations have not focused on adultery itself does not mean, of course, that adultery is never illegal. While adultery is not a federal crime, it remains listed as a crime in some states. Ensign’s home state, Nevada, is, ahem, not one of them. But, Edwards’ home state, North Carolina, is. A North Carolina “fornication and adultery” statute makes it a crime for a man and woman who are not married to one another to “lewdly and lasciviously associate, bed and cohabit together.” In a 2006 decision, a North Carolina lower court judge struck down this statute as unconstitutional, citing a 2003 U.S. Supreme Court ruling that a Texas ban on sodomy was unconstitutional. Therefore, the legal status of adultery statutes remains uncertain.

Nonetheless, they remain on the books in several states and could conceivably be enforced.

There are, of course, many reasons for a politician not to have an extramarital affair. Morally, most of us would agree that adultery violates one of the sacred vows of marriage. Politically, news of an extramarital affair can be devastating to a politician’s image and can cause an immediate drop in popularity with voters. Yet some marriages survive adultery, and some political careers withstand the public reaction to it. Sen. David Vitter (R-La.), for example, easily won re-election last year despite admitting to adultery. And President Bill Clinton remains a popular political figure despite his own extramarital affairs.

The investigations of Edwards and Ensign are reminders that, as if the moral and political reasons not to commit adultery are not enough, there is another reason for politicians not to do so: the law. Affairs and cover-ups cost money. Lots of it. And whenever politicians and large sums of money intersect, the murky federal campaign finance laws are implicated. Because of those laws, payments to the family of Ensign’s former mistress could result in criminal liability for Ensign. And payments to Edwards’ former mistress could have the same result for Edwards. Oh, what a tangled web.

C. Simon Davidson is a partner with the law firm McGuireWoods. Click here to submit questions. Readers should not treat his column as legal advice. Questions do not create an attorney-client relationship.