L.G.B.T. activists mobilized a fast and fierce campaign that included a protest outside the White House on Monday to say transgender people cannot be expunged from society, in response to an unreleased Trump administration memo that proposes a strict definition of gender based on a person’s genitalia at birth.

The existence of the draft memo, the administration’s latest effort to roll back the recognition and protection of transgender people under federal civil rights law, was reported by The New York Times on Sunday morning.

Within hours, the hashtag #WontBeErased circulated on social media. By Sunday evening, a rally for transgender rights took place in New York; another took place on Monday in Washington.

With the White House as their backdrop, speakers repeated the phrase “We will not be erased,” which has become a rallying cry against the proposal. The 45-minute rally, attended by what appeared to be at least several hundred people, repeatedly referred to the coming midterm elections and encouraged people to vote.