Answer: his breaking his campaign pledge not to raise taxes
Explanation:
President H.W. Bush promised during his campaign that under him, the U.S. government would not raise taxes in his famous quote, "Read my lips, no new taxes".
Upon getting into power however, he discovered a huge deficit left behind by Ronald Reagan that forced him to raise taxes. This alienated his supporters.
In his defence, he did try to limit taxes by vetoing over 35 bills during his administration.
