At the time, it all was more tawdry than momentous. A reality star invited a porn actress half his age to a hotel room after a round in a celebrity golf tournament. She arrived in a spangly gold dress and strappy heels. He promised to put her on television and then, she says, they slept together.

Yet the chain of events flowing from the 2006 encounter that the adult film star, Stormy Daniels, has said she had with the television personality, Donald Trump, has led to the brink of a historic development: the first criminal indictment of a former U.S. president.

Manhattan District Attorney Alvin Bragg has signaled he is preparing to seek felony charges against Trump; Bragg is expected to accuse him of concealing a $130,000 hush-money payment that Michael D. Cohen, Trump’s lawyer and fixer, made to Daniels on the eve of the 2016 presidential election.