When Sen. Al Franken (D-Minn.) reluctantly said this month he would resign over multiple groping allegations, he did it in a way that led his supporters to hope his resignation wasn't set in stone. He didn't say when he was resigning, and he clearly didn't want to.

“I am announcing that in the coming weeks I will be resigning as a member of the United States Senate,” Franken said. “There is a big part of me that will always regret having to walk away from this job with so much work left to be done.”

Franken's decision not to set a date for his resignation is rare and may even be unprecedented in Senate history, said political historian Robert David Johnson with Brooklyn College. But because he doesn't have a date set, it means he doesn't have to resign. "The date is key,” Johnson said.

Now it seems Franken's vague language about when he would resign has opened the door for a handful of Democratic senators to urge him, publicly and privately, to stay on.

“I definitely think he should not resign,” said Sen. Joe Manchin III (D-W.Va.) in an interview on CNN, explaining he thinks his colleagues rushed to judge Franken. Manchin said something similar in an interview with Politico, which reports at least two other Democratic senators say privately they regretted issuing statements that Franken should resign.

It's definitely possible for Franken to change his mind if he wanted to, because he hasn't actually resigned yet. He's just said he plans to. The politics of staying in office, though, is another story.

A resignation speech isn't the same thing as a resignation. A senator's resignation is not official until they submit a letter to their state's governor announcing the resignation and the effective date. After former Sen. Larry Craig (R-Idaho) was arrested in 2007 when he was accused of soliciting a man for sex in an airport restroom, he said he'd resigned -- then changed his mind and served the rest of his term, points out Cornell Law professor Josh Chafetz.

Franken has given no indication he will do a 180 and try to stay in the Senate. That would mean facing an ethics investigation into more than than half a dozen groping allegations spanning a decade, all but one of which he has not denied. Franken originally said he would cooperate with the Senate Ethics Committee's investigation, and in his resignation speech he said he was confident he would be vindicated.

Franken's office did not immediately respond to requests from The Fix about whether he has submitted that letter. But it is not likely that he has, given that Franken still does not have a date when he will resign. Once he sends in a letter with a resignation date, his resignation will be hard to stop.

Even without a set date, Minnesota's governor is acting as though Franken's resignation is a sure thing. Gov. Mark Dayton (D) announced Franken's temporary replacement, current Minnesota Lt. Gov. Tina Smith (D). But Smith could not take office until Franken actually steps down.

(Unrelated, but notable: If Smith stayed in her job as No. 2 in Minnesota, it would quell a political and legal battle there about whether her appointment could tip the current Republican majority of Minnesota's state Senate to the Democrats.)

Franken faces much more serious head winds when it comes to the politics of his resignation. Nearly all Senate Democrats still maintain he should resign, and pressure from his colleagues is what pushed Franken out in the first place.

That pressure seems unlikely to let up. A week after winning a Senate seat from Alabama when the Republican was plagued by sexual misconduct allegations, Senate Democrats do not seem to have any desire to fold Franken back into the mix.

The whole reason he is resigning is because Franken had just become too much of a political liability for a party trying to seize the moral high ground on THE social conversation of the day. Franken was facing a drip, drip, drip of allegations, and he awkwardly tried to maintain innocence while apologizing for groping he said he could not remember.

Senate Minority Leader Charles E. Schumer (D-N.Y.) was instrumental in urging Franken to quit, and Schumer stands by that decision today. Democrats would have some serious explaining to do for why they think Franken is suddenly fit to serve in the Senate when they didn't just last week.

“Schumer and the vast majority of the caucus like Sen. Franken and will miss him,” said a Senate Democratic leadership aide, “but did what they felt was best and stand by it.”

Part of the reason Franken's resignation is so open to interpretation is because everything about it is so rare, said Johnson.

Senators resigning is a regular occurrence, but normally it's to move to another office or to end their term early to give the newcomer a leg up. Since World War II, only three other senators have resigned over scandal. Those senators were also facing ethics investigations or, in at least one case, potential expulsion.

Franken made the decision to resign based on political pressure from his colleagues. So is it possible he could change his mind if his colleagues also do? Yes. But it's not likely, since most Senate Democrats have been pretty clear they want Franken gone, ASAP.