惩一儆百；以儆效尤
make an example of
The teacher made an example of the boy she caught cheating.
The judge imposed a tough sentence to make an example of the car thieves.
　
哗众取宠
camp it up; play to the gallery
Amateur actors often camp it up, trying to be more dramatic.
He peppers his speeches with humor and wisecracks about his opponent, clearly playing to the gallery.