It's certainly the case that politicians in various countries have found ways to allude to racist or anti-minority sentiments without literally saying anything racist or beyond the pale. No doubt many of their audience in such cases are simply agreeing with the literal meaning of what is said, and not with the uglier implications behind it - but the more overt racists get the idea.

Of course it's not always easy to tell whether such statements are really intended as dogwhistling or if the politician really didn't mean to imply more than what he literally said. In Trump's case, it's probably a safe bet that most of the time he's not thinking ahead enough to do anything that subtle. And more generally, I'm usually inclined to adhere to the good old principle of not ascribing to malice what can be adequately explained by incompetence. But there are definitely cases where the description is appropriate.