Definition from Wiktionary:
Kinsley gaffe (plural Kinsley gaffes) ( US politics) A mistake whereby a politician inadvertently says something truthful which they had not meant to reveal.
Ed Driscoll posts at Instapundit a Jim Treacher quote (behind paywall), revealing foggy Joe Biden committing a classic Kinsley gaffe.
CBS “journalist”: Are you confident that there will be a peaceful transfer of power, January 2025?
Joe: If Trump wins, no, I’m not confident at all.
[EXCRUCIATING PAUSE AS HE REALIZES WHAT HE JUST SAID IN FRONT OF THE WHOLE WORLD]
I mean, if Trump loses, I’m not confident at all.