A woman who worked on Donald J. Trump’s 2016 presidential campaign sued him in federal court on Monday, alleging that he forcibly kissed her at a campaign event in Florida months before the election.

In the lawsuit, the woman, Alva Johnson, who is black, also accused the president’s campaign of discriminating against her by paying her less than her white and male colleagues.

She joins more than a dozen other women who have publicly accused Mr. Trump of sexual misconduct.

According to the lawsuit, which was filed in United States District Court in Tampa, Fla., Mr. Trump kissed Ms. Johnson without her consent on Aug. 24, 2016, in Tampa as he got out of a recreational vehicle during a campaign stop.

The encounter began when Ms. Johnson, who was in the RV, spoke with Mr. Trump as he made his way to the door of the vehicle, according to the suit. She told him that she had spent months on the road working for him and offered words of encouragement.