Democratic Senate candidate Graham Platner was heckled Tuesday for sexual depravity and called a “freak” when he arrived at a meeting of Senate Democrats on Capitol Hill.

A chorus of 30 protesters jeered the presumptive Democratic nominee in Maine about the hookup app KiK — a site known for facilitating teen hookups — when he was in his 30s.

The protesters, who did not identify themselves with a particular organization or political side, gathered outside the Democratic Senatorial Campaign Committee headquarters on Capitol Hill. They waved signs that read, “Delete your KIK,” “Platner messaged minors,” “Platner is a fraud,” and “Why does Platner still have KIK?”

They also chanted, “Port-a-potty Platner,” “Hey-hey-ho-ho P-Hustle’s got to go,” “Graham shamed Maine,” “Delete your KIK” and “Platner is a freak.”

The account used the name Graham Platner and the handle associated with his Reddit and Instagram posts, “Phustle,” and “Phustle0331.”

Democratic lawmakers who met with Mr. Platner were also heckled by a protester with a bullhorn who asked why Mr. Platner’s KiK account is still active. The protester called out by name Sen. Amy Klobuchar of Minnesota, Sen. Adam Schiff of California and Sen. Edward Markey of Massachusetts.

“Did you ask Graham Platner if he could state unequivocally that he’s never communicated with a minor on Kik?” blared from the bullhorn.

The KiK profile was created in June 2016, when Mr. Platner was about 31 years old.

The revelation about the KiK account comes after Amy Platner recorded a video defending her husband and expressing anger at media reports that exposed his sexting with several women.

Mrs. Platner alerted her husband’s campaign staffers about the sexually explicit texts in the days before the Democrat announced his Senate bid, when the party was scanning his past for any dirt that political opponents might find.

Mr. Platner was on Capitol Hill to shore up support from his party’s establishment, which opposed his candidacy before he surged in the polls, forcing the establishment’s pick, Maine Gov. Janet Mills, to suspend her Senate campaign.

It is a marquee race where Democrats have their best shot at flipping a seat. The seat is held by longtime GOP Sen. Susan Collins.

Senate Minority Leader Charles E. Schumer voiced support on Tuesday for Mr. Platner, but refused to address mounting controversies surrounding the candidate.

Pressed about Mr. Platner’s sexual exploits, Mr. Schumer responded: “I met with Graham Platner today. We’re going to beat Susan Collins and take back the Senate.”

Mr. Platner previously weathered backlash for a Nazi-symbol tattoo on his chest, which he covered up after announcing his Senate run. He has also been blasted for several posts on his now-deleted Reddit account that include topics such as sexual assault and military veterans.

In 2013, he posted on Reddit: “How about people just take some responsibility for themselves and not get so f——- up they wind up having sex with someone they don’t mean to?”

He also mocked a Purple Heart recipient, calling the wounded soldier a “dumb motherf——-” who “didn’t deserve to live.”

He deemed all police officers “bastards,” agreed with posts calling rural White Mainers “racist and stupid,” and asked, “Why don’t Black people tip?”