What would a Franken ethics investigation mean?

After a Los Angeles radio anchor accused him of sexual misconduct during a 2006 USO tour, Minnesota Sen. Al Franken faced a storm of criticism — and calls for an ethics investigation — from fellow senators.

Senate Majority Leader Mitch McConnell, R-Ky., and the top Democrat, Chuck Schumer of New York, both called for an inquiry.

Franken, a Democrat, said he would cooperate with an investigation. Thursday morning, Leeann Tweeden posted a photo showing his hands over her breasts, and said the senator forcibly kissed her during a 2006 entertainment tour with the USO.

As the senators weigh what's next for Franken, here's what you need to know about the work of the U.S. Senate Select Committee on Ethics.

This would not be a criminal investigation

A probe by the ethics committee stays within the Senate. Both staffers and senators can be investigated. It's not a legal or judicial process, but a professional disciplinary one.

"It is strictly an internal Senate process, and it is very political in nature," said Ron Elving, an editor and correspondent on NPR's Washington desk.

The ethics committee was set up in the 1960s. Before then, there wasn't a standard way to discipline people in the Senate. Today, it has six members: three Republicans — chair Sen. Johnny Isakson of Georgia, Sen. James Risch of Idaho, Sen. Pat Roberts of Kansas — three Democrats — vice chair Sen. Christopher Coons of Delaware, Sen. Jeanne Shaheen of New Hampshire and Sen. Brian Schatz of Hawaii.

The case of Sen. Bob Menendez, a New Jersey Democrat, illustrates the separation between the ethics committee and the legal system. Hours after a judge declared a mistrial in his corruption and bribery case on Thursday, the ethics committee announced it would resume its own investigation into the allegations.

Its investigations can have serious consequences for members

The ethics committee can recommend expelling a member,and sends its recommendation to the full Senate. Two-thirds of the Senate must vote in favor of expulsion for a member to be expelled. The Senate hasn't kicked out a member in more than a century. According to NPR: One senator was expelled for treason in 1797, and 14 were expelled in 1861 and 1862 for aiding the Confederacy in the Civil War.

The committee can also censure a member, which amounts to a formal scolding for their actions.

There have been only nine votes to censure senators, NPR reports. The most recent was in 1990, when Minnesota Republican Sen. David Durenberger was disciplined for bringing "dishonor and disrepute" to the Senate for financial misconduct, the Senate said at the time.

Durenberger was accused of "improperly enriching himself through a book publishing deal, a condominium swap and acceptance of free limousine service from special interest groups," The Washington Post reported at the time.

Parts of the investigation would be public

The investigation would include collection of any evidence, as well as testimony in front of the ethics committee, which has the power to subpoena witnesses.

While the ethics committee would likely deliberate in private, it's also likely that much of the testimony would be televised, Elving said. In the Franken case, that could include both the senator and his accuser, as well as others who may have known about the alleged incidents.

Some documents associated with the probe could also become public.

It's very rare for the Senate to investigate sexual misconduct

The ethics committee hasn't investigated sexual harassment or assault allegations in 25 years, Axios reports.

In 1992, days after Oregon Republican Sen. Bob Packwood won reelection, The Washington Post published a story that said Packwood had made unwanted sexual advances toward several women. More came forward with allegations after the story was out.

The ethics committee didn't vote to expel Packwood until three years later, and he resigned before the official expulsion.

It's also uncommon for the committee to investigate actions that happened before a senator took office

Elving, a veteran political reporter, couldn't recall a time when the ethics committee investigated a senator for their actions before taking office. Franken's alleged actions occurred two years before he was first elected to represent Minnesota in the Senate.

However, if a Franken ethics investigation were to move forward — and if Alabama Republican Roy Moore wins a Senate seat next month — the ethics committee could very likely have have two such investigations going at the same time.

Multiple women have accused Moore of sexual assault and misconduct. Some of those women were minors at the time. Moore has denied the allegations, but several top Washington Republicans have said he should drop out of the race.

McConnell, the Senate Majority leader, says Moore will face an ethics probe if he wins the special election. (McConnell, however, is not on the ethics committee.)