Tina Smith greeted former Vice President Walter Mondale at MSP Airport on the way to D.C. for her swearing in. On the left is Smith's father. (Star Tribune/The Minnesota Star Tribune)

WASHINGTON – Al Franken resigned from the U.S. Senate on Tuesday, an unceremonious end to the political career of Minnesota's most well-known elected official.

"Serving the State of Minnesota in the U.S. Senate has been a privilege and an honor," Franken wrote in his letter of resignation to Gov. Mark Dayton. "I am grateful to Minnesotans for their giving me the chance to serve our state and our nation, and I am proud to have worked on their behalf."

The resignation became official at noon on Tuesday. That means Minnesota will have just one U.S. senator, Amy Klobuchar, for roughly 24 hours. Franken's replacement, Lt. Gov. Tina Smith, will be sworn in shortly after Congress reconvenes on Wednesday at noon for a new session.

Franken's resignation, which he announced in December, followed allegations by more than a half-dozen women that he had touched or kissed them without permission. Franken initially tried to weather the ensuing controversy, but decided to step down after several dozen of his fellow Democratic senators demanded he do so before an ethics investigation played out.

Franken's resignation letter, a terse 70 words long, made no mention of the circumstances of his departure.

Franken has said little about his post-Senate plans, beyond stating that he intends to remain engaged.

In Minneapolis last week, his first public appearance since the allegations broke in November, he told about 300 supporters, family members and friends that he would continue to work on issues from climate change to net neutrality.

"I may be leaving the Senate, but I'm not giving up my voice," he said.

The former "Saturday Night Live" writer and radio host was elected to the Senate in November 2008 but not seated until eight months later, after a recount and legal decision determined he won by just 312 votes out of millions cast. His victory gave the Democrats a 60-vote, filibuster-proof majority under President Barack Obama in the upper chamber.

Once Franken vacates the office, Smith will take on the twin tasks of representing Minnesota and running for the seat, which is on the ballot in November.

One Republican is in the race already, state Sen. Karin Housley of St. Marys Point. And former U.S. Rep. Michele Bachmann said in a recent TV interview that she has been asked to run and is considering it.

Smith officially resigned as lieutenant governor on Tuesday, and will be replaced by state Sen. Michelle Fischbach, R-Paynesville, who as president of the Senate is next in line of succession. Her elevation to Dayton's number two post has created uncertainty in the Legislature, with Fischbach hoping to simultaneously retain her Senate seat but probably facing a legal challenge if she decides to do so.

Nationally, Smith's entry to the Senate will be overshadowed by the swearing in of Doug Jones, the first Democrat to represent Alabama in 25 years. His close election victory over Republican Roy Moore increases the Democratic caucus from 48 to 49. That leaves the GOP majority so narrow that Senate Majority Leader Mitch McConnell has signaled 2018 will be a more bipartisan year, given that it will be more difficult to pass legislation along strictly partisan votes. Jones is also more likely to cross party lines as a moderate Democrat in a conservative state.

Maya Rao • 202-662-7433

FILE: Sen. Al Franken chats with incoming senator Tina Smith. (The Minnesota Star Tribune)

On her way to D.C. Tuesday for her swearing in, Tina Smith and her father, left, greeted former Vice President Walter Mondale at Minneapolis-St. Paul International Airport. She will be sworn in Wednesday around noon. (Star Tribune/The Minnesota Star Tribune)