Who may be on the shortlist to replace Al Franken in the Senate

Gov. Mark Dayton, a Democrat, will appoint an interim senator.

— -- Minnesota Sen. Al Franken announced Thursday that he will resign from the Senate in the coming weeks, in a speech on the Senate floor.

"This decision is not about me, it's about the people of Minnesota," Franken said. "It has become clear that I can't both pursue the Ethics Committee process and at the same time remain an effective senator for them."

A number of women have accused Franken of unwanted touching. He denied some of the allegations and said he remembers some of the encounters "very differently."

On Wednesday a majority of his Democratic colleagues in the Senate, including Minority Leader Chuck Schumer of New York, said it was time for him to step aside.

If Franken leaves Congress before the end of May, that will prompt a special election in Minnesota next November, with a regularly scheduled election for the seat in November 2020.

Minnesota Gov. Mark Dayton, a Democrat, will appoint an interim senator.

But under state law, if a seat is vacated less than 11 weeks before the next regularly scheduled primary, the special election will be scheduled for the second November election after the vacancy. The next primary is set for Aug. 14, 2018, so if Franken vacates his seat after May 29, an election will not be held until 2020, and his appointed replacement will serve until January 2021. That is the regularly scheduled end of Franken's term, so whoever wins the 2020 election will serve a full six-year term.

After Franken's announcement Thursday, Dayton said he has not yet decided whom he will appoint to fill the upcoming vacancy but expects to make his decision known in the "next couple of days."

Democratic strategists in Washington and Minnesota told ABC News they expect Dayton will chose a woman.

"I think it would be a great opportunity for us," Alex Boutrous, the president of Minnesota's Young Democrats, told ABC News. "Especially in light of having a male senator who is stepping down because of sexual harassment allegations, to have a woman replace him would make a statement that not only do we believe women but we believe in their leadership and we want to empower them to take this role on."

When Minnesota's senior senator, Amy Klobuchar, was elected in 2006, she was the first woman elected to the Senate from the state.

Minnesota's Lt. Gov. Tina Flint Smith, is likely at the top of Dayton's list, several sources have said. She was his chief of staff before she was his running mate.

However, an interesting wrinkle in state law — under which the Minnesota Senate president becomes lieutenant governor should the lieutenant governor leave — could make Smith's prospects less likely. The current state Senate president is a Republican.

Rep. Betty McCollum, a longtime member of the congressional delegation who represents part of St. Paul, could be at the top of the list.

Other experts have suggested, though, that Dayton may want to send more a progressive message and perhaps choose an up-and-comer such as state Rep. Ilhan Omar.

Elected last year, Omar is the highest-ranking Somali-American elected to office in the country, and she would be the first Muslim to serve in the U.S. Senate. She was featured on "The Daily Show With Trevor Noah" last year and said, "I am America's hope and the president's nightmare." Her appointment could be seen as sending a message from the state.

Another possibility, despite his gender, is Rep. Keith Ellison, who is the first Muslim elected to the House. An African-American who has close to ties to progressive, grass-roots activists and a leadership role on the Democratic National Committee, he is likely on the shortlist.

Others whom Minnesota political experts have floated include Lori Swanson, the state's attorney general since 2006; Rebecca Otto, the state's auditor, who is running for governor but is not seen as a front runner; Erin Murphy, a longtime state lawmaker who is also running for governor;, and Rep. Tim Waltz.

Waltz is more of a moderate and is one of many Democrats jockeying for the party's nomination for governor next year. He is largely considered the favorite in that race to replace Dayton, so people familiar with the state's politics think he would be less likely to accept the Senate appointment.

His running mate, Peggy Flanagan, however, could be an interesting choice. A young Native American political activist, she spoke last year at the Democratic National Convention.

"I would love to see [Flanagan] taking on a bigger leadership role in our state, whether that is as a senator or a lieutenant governor," Boutrous said. "But I think, since we have so many great women, I think pulling from women that are not currently on a ticket [in the state] is what I would proposing."

"Thinking about how many incredible women of color and indigenous women we have in elected leadership in Minnesota, I think it is a great opportunity to take that one step farther and appoint ... a woman of color or an indigenous woman to the Senate for Minnesota," she added.

ABC News' Veronica Stracqualursi contributed to this report.