cut the ground from under (someone)
To suddenly cause problems for someone. I plan to cut the ground from under the prosecutor with this line of questioning.
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.