I think Clinton is a serial liar too. She mainly lies to protect her own skin and to make herself look good, which are things that virtually every politician (and most people, really) do. I am not trying to understate it; I think she is quite dishonest. She lies and hopes not to get caught.
But let's apply the same standard to Mr. Trump. He lies to make himself look good. He lies as a business practice. He lies about his business practices. He lies about basic obectively verifiable facts...constantly.
At best, and I mean absolute best for Trump, the question of honesty is a wash. But I think the bravado with which Trump tells absolute whoppers is a character trait that is fairly unique: he lies and doesn't care if he gets caught because he has little to no regard for the truth or for the people he is lying to.