CBS/YouGov poll of adults:
I am a strong Trump supporter, period - 19%
I am a Trump supporter, but to keep my support, he has to deliver what I want - 22%
I am against Trump now, but could reconsider him if he does a good job - 19%
I am strongly against Trump, period - 40%
Not exactly an approval poll, but if you grouped the people who say they support him and those who are against him, it's 41/59.
Also, deporting illegal immigrants and banning Muslims are more important to Trump supporters than cutting taxes.
And job creation is vastly more important to Trump supporters than either of those issues...