She is a lying traitor and should be rotting in prison. No one has any reason to support her. A woman is also not capable of leading the world's most powerful country. Trump has a lot to gain for exposing all her lies and false promises. More and more people are opening up to the truth.
I think the majority of Trump supports are also haters of Clinton. Not only are they opposing rivals, but there are many reasons people choose not to support Hillary, and unfortunately that gives Trump an advantage. Also, given how radical and unlikeable Trump is, it will be hard to turn his supporters against him. If they were with him before, they will be even more with him now.
Yes, Trump could definitely gain supporters by attacking Clinton. For a lot of people, when a candidate attacks their opponent, people are turned off by their aggressive attitude. However, with Trump, it seems that no amount of rudeness and aggression can turn people away from him, due to the pitiful choice of candidates the American people have to chose from. By attacking Clinton, Trump can perhaps expose some of her flaws and weaknesses, thereby making people more angry at her, and less angry at Trump. The worse Clinton appears, the better Trump appears.
Donald Trump can absolutely gain on his opponent Hillary Clinton by attacking her and her policies. The Clinton's are extremely gifted politically and are loved by many and hated by nearly the same amount. I believe that the only platform Trump can run on is an anti-Clinton brand of politics.
Trump has been attacking Clinton, but he has little to gain. There is a wealth of information on her, and those that do not like her have already made up their mind. These people tend to be partisan, and nothing Trump says will change their mind. Conversely, those that support Clinton and her policies will not be swayed to vote against her.