On Thursday morning, Los Angeles-area radio host Leeann Tweeden accused Sen. Al Franken (D-Minn.) of sexually harassing her on a USO tour in 2006. She alleges that Franken wrote a skit in which she was supposed to kiss him, and then pressured her into "practicing" the routine, during which he forcibly kissed her. Then, while Tweeden was asleep on the flight back home, Franken posed for a horrifying picture where he appears to touch her flak jacket over her breasts.

Franken issued an apology, and when that was widely condemned, issued another one, admitting that the picture was "completely inappropriate," and agreeing to subject himself to an ethics investigation.

Several other Senate Democrats have already signed onto this call for an ethics investigation. But that is not good enough. Al Franken needs to resign.

If there were any reason to give Franken the benefit of the doubt and allow an investigation to proceed, that would be one thing. But the photo — in which Franken is either committing sexual assault, or is millimeters from doing so, on an unconscious woman — ends any doubt. That behavior is completely disqualifying for a U.S. senator — or anyone else, for that matter. He has to go.

Democrats must demonstrate their moral seriousness on this issue. Right now in Alabama, Roy Moore is attempting to win election to the U.S. Senate despite a seemingly never-ending deluge of woman from his past alleging that he sexually harassed or assaulted them when they were teenagers and he was a 30-something district attorney. Democrats are eagerly and rightly seizing the political opportunity to push their own candidate, Doug Jones, and win the seat.

The transgressions of Franken and Moore are different, no doubt. But you simply cannot denounce Moore and protect Franken. It is undeniable that Franken's behavior was grotesque. He must resign, and Democrats must demand that he do so.

Getting rid of Franken would demonstrate that Democrats take sexual harassment seriously, and aren't just opportunistically using feminist principles to take down their political enemies while setting them to the side when one of their own is under attack. Indeed, it would go no small distance to making up for the tawdry history of the late 1990s, when some feminists like Gloria Steinem cynically leveraged their cultural credibility to excuse President Clinton for an inherently abusive relationship with a 21-year-old subordinate.

Democrats can't even muster the excuse that getting rid of Franken would hand the seat to a Republican. He is not up for re-election until 2020, and the Minnesota governor is Democrat Mark Dayton. If Franken resigns, then he would simply be replaced by another Democrat from the state — Keith Ellison or Betsy McCollum, for example.

Then there's the fact that Franken is 66 years old — already past traditional retirement age. This isn't somebody with decades of a bright and promising career ahead of him. Indeed, moving someone else up into the seat would open up spots further down the ranks and advance the careers of several younger people — something the Democrats, with their generally elderly leadership, need quite badly.

The last several months have seen an often wrenching parade of past sexual abuses being dredged up — bringing into the open pain that was secret, hidden, and private. It can seem particularly awful when the perpetrator is someone who was supposed to be "one of the good guys." But it's also a necessary process — a lancing of a festering cultural boil that was very obviously badly overdue.

That is the final reason to ax Franken: to set an example. If we as a people demonstrate that this sort of behavior means an instant end to one's political career, future up-and-coming politicos — and the broader population in general — might just internalize the lesson, and stop abusing people.