I would like you to suggest a more apt/suitable idioms and expressions in the following senses:
Everybody knew it would eventually happen at the end of the day. After waiting for some time like a year or so, he/she makes a big/major mistake as Donald Trump did by urging ban on all Muslims coming to the U.S.
Some people make an irreparable/fatal mistake as Rick Perry did in the presidential debate in 2011. He couldn't remember which three agencies he would eliminate as POTUS and it was the major turning point for his doomed candidacy.
An idiom like drop the ball doesn't necessarily convey the meaning as it doesn't sound like the mistake is as big/serious/fatal as the above-mentioned ones based on the below definition:
Make an error; miss an opportunity. For example, She really dropped the ball when she forgot to call back, or He dropped the ball, turning down their offer.
[American Heritage Dictionary]
Are there any more suitable idioms/phrases that can signify or express an once-(or twice)-in-your-lifetime mistake that is so serious and rare that it may change the course of your life?