In 2004, Howard Dean, then a viable candidate for the Democratic presidential nomination, let out an enthusiastic yell during a campaign event. It ended his candidacy.
In 2013, Marco Rubio, considered a possible Republican presidential contender, drank water during a speech. It marked the end of his national political career.
In 2024, Donald Trump appeared to promise to end elections in the US if elected, and was cheered. He's polling roughly evenly with his opponent.