Scandal-hit US Senate candidate Graham Platner -- whose insurgent rise has drawn comparisons to President Donald Trump -- denied a sexual assault allegation Monday that threatens to derail one of Democrats' best chances of flipping a Republican-held seat.

Politico reported that Jenny Racicot, a 41-year-old Maine resident who previously dated Platner, accused him of forcing her to have sex in late 2021 despite repeated objections.

Platner, a Marine veteran, oysterman and political newcomer who won the state's Democratic primary last month, rejected the allegation.

In a video message posted to X after the report was published, Platner called the allegations "troubling, serious and false."

"Regardless of the inaccuracy of the reporting, but mindful of the political reality it will inflict, we are taking the time to reflect on the best path forward for the state that I love, the people that I love, the movement I belong to, and the goal of defeating Susan Collins," he went on, referring to the Republican incumbent.

"Those were the goals when we launched this campaign, and they remain my goals today."

The allegation lands at a perilous moment for Democrats, who view Maine as a central battleground in their effort to regain control of the Senate in November's midterm elections.

Collins, a six-term Republican and one of her party's few remaining moderates in Congress, is among the Democrats' top targets.

Platner's victory in the Democratic primary was hailed by supporters as proof that a blunt anti-establishment message could break through with voters frustrated by cautious, establishment politics.

But his campaign has also alarmed some Democrats who fear his personal baggage could make it harder to defeat Collins in a state where independents and moderate voters often decide elections.

Politico said Racicot alleged that Platner entered her rural Maine home uninvited while deeply intoxicated and forced himself on her.

The latest report follows earlier controversies over old online comments, sexually explicit messages, a tattoo resembling a Nazi symbol that Platner later covered up, and allegations that he had mistreated women.

Platner has acknowledged past struggles with undiagnosed PTSD and alcohol abuse, but has denied physically harming former partners.

His supporters argue that his flaws are part of a redemption story and that voters are drawn to his authenticity.