cut the ground from under(neath) (one's) feet
To suddenly cause problems for one. I plan to cut the ground from underneath the prosecutor's feet with this line of questioning.
cut the ground from under someone
or cut the ground from under someone's feet
If you cut the ground from under someone or cut the ground from under their feet, you make their ideas or opinions seem less impressive, often by doing something unexpected. The sudden announcement was seen by many as an attempt to cut the ground from under the president's feet.
cut the ground from under someone's feet
do something which leaves someone without a reason or justification for their actions or opinions. informalcut the ground from under somebody/somebody’s ˈfeet
suddenly spoil somebody’s idea or plan by doing something to stop them from continuing with it: When he announced that all my figures were out of date, he really cut the ground from under my feet.