As if the reemergence of the Clintons and their apparently-not-dead-yet campaign against Barack Obama weren't bad enough, the Democrats now have another big headache emerging after the world's longest primary season: John Edwards, who admitted to ABC News today that he had an extramarital affair with a woman who worked on his latest Presidential campaign, novice filmmaker Rielle Hunter.

The Dems dodged a bullet by not nominating Edwards, it seems. And how irresponsible was it of him to keep running, knowing he had this scandal that could explode in his face at any moment?

Edwards’s confession is a sad end to what was, for a time, the most progressive major candidacy of the primaries. Edwards served an important purpose until he dropped out, reminding Hillary, Obama, and the voters about the enormous, corrupting influence of corporate money on both parties, and about the shame of widespread poverty in the most affluent country on Earth.

Sadly, that message will now be buried in scandal. The gory details of Edwards visiting Hunter and her baby at 2:40 in the morning on July 20 don’t help. (Edwards reportedly ran away down a hall and ducked into the men's room.)

The interview airs tonight on Nightline. In it, Edwards assures Bob Woodruff that he is not the father of Hunter's baby, as the National Enquirer alleges. (Is there any doubt that rightwing radio hosts are wearing a hole in their old LP copies of "Love Child"?) Former campaign aide Andrew Young has claimed paternity. Not exactly a charming tableau. And, weirdly, Hunter has been shuttling around to different homes in North Carolina and California, living under an assumed name since she became pregnant. There is no positive spin on that.

At least Edwards says he told his wife, Elizabeth, about the affair back in 2006. But why in the world did they both go forward with the campaign in March 2007, when Elizabeth got the terrible news that the cancer was terminal? He should have rededicated himself to his marriage at that point, not to the campaign trail.

One of the most appealing things about Edwards was always his marriage to Elizabeth. The news is a low, low blow to a great woman who has been an incredible support to him, a terrific advocate for health care and families, and a role model and inspiration for cancer survivors. She also has a fan base of her own more devoted than Hillary supporters at peak umbrage.

You have to wonder if there is a gene for philandering closely linked to the political ambition gene.

Although conservatives will make hay out of the scandal, Edwards doesn't come near to topping Newt Gingrich, who served his wife divorce papers in her hospital bed. Nor, for that matter, does McCain have the high ground after his treatment of his first wife, and his serial verbal abuse and sexist mockery of his current spouse.

Still, the last thing the Democrats need is more soap opera drama. It's an unfortunate coincidence that Edwards's admission broke on the same day that the Obama campaign announced Bill Clinton will get a high-profile slot to address the convention in Denver--right before the vice presidential candidate on Wednesday night. One man's philandering only serves to remind us of the other.

Hillary is encouraging her supporters who want to cast their "cathartic" ballot for her, and Bill is all over the airwaves demurring on the question of whether Obama is ready to lead. Maybe the Edwards news will convince the Obama camp to stop placating the Clintons by coddling Bill and try to make a clean break of it. Obama, at least, still seems to have an admirable, intact marriage.

In fact, Obama could take a cue from Bill Clinton at the 1996 convention, when news about Dick Morris's carrying on with prostitutes broke. The Clintons are tough. They pushed Morris under the bus immediately. (Only later did we learn how Bill and Dick shared libidinous adventures).

Obama would be smart to run as far and fast as he can from the boys-will-be-boys wing of the party.