Twenty-Five now
The 25th amendment to the U.S. Constitution has never been invoked. Article 4 of this amendment gives the power to the cabinet, by a simple minority, to relieve from authority (not technically from office) a president deemed unfit to carry out his duties. It would take effect immediately on being invoked. Unfortunately, to be sustained, it would need approval — by a two-thirds majority in both the House and Senate, but votes on this could take a while. So, at least temporarily, it would put the brakes on the madness this president is imposing on our nation and the world.
It could not be more clear if Trump were to appear in public in a neon clown suit — he is patently unfit. And he has demonstrated again and again that there is no limit to this madness, up to and including ordering nuclear strikes, when his military runs out of conventional munitions, and a Congress horrified by his unhinged actions declines him more funding.