Crying wolf all the time
The President of these United States is a racist, and he does not care about the suffering of black people. He plays to racist elements in his party. He is is very dim-witted, far below the standards needed for the oval office. He is a rampant misogynist and his policies do severe harm to women. He is a serial liar who has overseen multiple very serious scandals. He was elected despite losing the popular vote to a much more qualified candidate and stole the presidency. I am of course, talking about George W. Bush.
Note: I don't actually believe in anything I wrote in the opening paragraph. I cannot believe I have to actually be this explicit, but sarcasm is pretty much dead in our politics today.
Democrats, liberals and some "Never Trump" conservatives cannot understand why Donald Trump's base is not only sticking with him, but many of them now support him more than ever. This is because the attacks on Trump are things we have heard hundreds of times before about many other Republicans. The same things being said now about Trump now would have been said about Ted Cruz, Marco Rubio, Jeb Bush, Mike Huckabee, John Kasich and Rand Paul. Many of the same things were said about Mitt Romney and George W. Bush. This is why Republicans do not take the attacks on Trump seriously.
For the sake of argument, let's say Trump is uniquely terrible. The problem is that liberals have cried wolf so many times that they do not have any credibility any more. Republicans have heard these attacks so many times that the automatic reaction is to ignore the attacks. Now, Trump is certainly a unique personality, in ways that are both good and bad. But Trump is largely a reaction to the Democrats bad-faith attacks on Republicans over the last few decades. If you are going to whip out the same boring "racist, sexist, bigot" handbook every time, Republicans said, we're going to pick the guy who is not afraid to fight back hard.
Let's be real here: It was the excesses of the Left that elected Trump in the first place.