US Senator Al Franken said on Thursday he will resign in the face of multiple accusations of sexual misconduct against him, becoming the second prominent Democrat to be forced out in a week over the snowballing harassment allegations convulsing the country.
Franken -- a former comedian who made his name on the popular late-night show "Saturday Night Live" -- announced his decision in an emotional yet somewhat defiant address from the floor of the Senate, where dozens of his colleagues had demanded he step down.
The once-popular 66-year-old Minnesota lawmaker apologised last month after acknowledging one incident of misconduct, vowing to work to regain public trust.
But with six other women now reportedly coming forward to accuse Franken of touching them inappropriately, a chorus of Democratic senators said it was time for him to go.
"Serving in the United States senate has been the great honour of my life," Franken said, with only a handful of his colleagues in attendance.
"I know in my heart that nothing I have done as a Senator -- nothing -- has brought dishonour on this institution," he added, noting he was shocked at the allegations against him, and painting himself as "a champion of women."
"Nevertheless, today I am announcing that in the coming weeks, I will be resigning as a member of the United States Senate."
Franken also took a parting shot at Donald Trump -- who himself has faced multiple allegations of sexual harassment -- and at Alabama Senate hopeful Roy Moore, who has received the president's endorsement despite being accused of molesting several teenaged girls.
"I, of all people, am aware that there is some irony in the fact I am leaving while a man who bragged on tape about his history of the sexual assault sits in the Oval Office, and a man who repeatedly preyed on young girls campaigns for the Senate with the full support of his party," Franken said.
The first allegation against Franken -- for which he has apologised -- was made by sports broadcaster and former model Leeann Tweeden, who said he forcibly kissed her, and touched her without consent as she slept, during a 2006 tour entertaining US troops deployed in Afghanistan.
But several other women have since come forward to say he groped them, triggering the revolt by female lawmakers against their own colleague.
In a well-coordinated social media attack, 12 of the Senate's 16 Democratic women took to Twitter or Facebook to demand Franken's resignation.
Senator Kirsten Gillibrand's Facebook post sounded the opening salvo on Wednesday, as she declared that the nation -- and Congress -- faced a "moment of reckoning" regarding sexual misconduct.
"We should demand the highest standards, not the lowest, from our leaders," she said.
Seventeen male colleagues followed, including top Democrat Chuck Schumer, who heaped major pressure on Franken by issuing a statement saying he should step down "immediately."
It marked a dramatic and sudden show of unity against one of their own in the 100-member chamber, where the Republicans hold a slim majority.
"We must commit to zero tolerance," Senator Heidi Heitkamp said in a tweet. "And that means Senator Franken should step down."
With support from fellow Democrats vanishing, Franken had a stark decision to make: heed the calls to leave, and allow the party to close ranks and try to gain the moral high ground amid a tidal wave of sexual harassment allegations that have lashed the political world -- or stay and fight.
Franken's resignation came just two days after Democrat John Conyers, the longest-serving member of Congress, left the House of Representatives after several female former staffers accused him of sexual misconduct.
And it follows a wave of accusations of harassment against titans in the worlds of entertainment, the media and politics, which began with claims targeting movie mogul Harvey Weinstein earlier this year.
Rocked by the unfolding scandals, the Senate and House both voted to make anti-harassment training mandatory for all lawmakers and staff. (AFP)