I think most people have forgotten that. It's the 25 years of mud-slinging, not one failed policy initiative.
People have been saying, hearing and repeating bad stuff about Hillary Clinton since the '92 campaign, and when even sympathisers agree with some of the main points, it sticks.
When you think about it, 25 years with a national political profile is a very long time. It's the time between Reagan's A Time For Choosing speech and the end of his second term, or between Nixon making a name on the HUAC and his resignation.