Pew Research did the study and the math:

The new Pew Research Center survey of 3,455 U.S. adults, conducted Sept. 22-28, also finds that majorities of Americans say that since taking office in January, Trump definitely or probably has improperly used his office to:

• Punish those who say things he does not like (66%)
• Enrich himself or his friends and family (61%)
• Encourage federal investigations of his political opponents (62%)
Similar majorities say Trump definitely or probably has not set a high moral standard for the presidency (64%), improved U.S. standing around the world (60%), run an open and transparent administration (60%), or improved the way government works (59%).

Even a good chunk of Republicans think Trump has abused his office:

Among Republicans, 42% say Trump has improperly used his office to punish those who say things he doesn’t like, while a nearly identical share (40%) say he has improperly encouraged federal investigations of political opponents. About three-in-ten Republicans (31%) say Trump has improperly used the office to enrich himself or his family or friends.

Sadly, 70% of Republicans still think President Felon is doing a heckuva job:

At least seven-in-ten Republicans say that in his current term, Trump definitely or probably has improved the way government works (74%), improved the country’s standing in the world (73%) and run an open and transparent administration (70%).

(H/T Sarah Posner)