Politifact ranked all the candidates on their honesty based on their statements.
Guess what ... Clinton actually when fact checked is the most honest. Sanders was no.2, Cruz and Trump were basically lying out their ass.
The Republicans have been smearing Hilary for 15+ years because they're afraid of her, they know the Clinton presidency was a very good one and they need to attack her and brand her in 1500 different ways.
Also a politican changing position on something over the course of 15 years is not "lying". It's simply changing a position which I would hope any sensible person would do, I don't believe everything exactly the same way as I did 20 years ago.