Put yourself in their position.

For the sake of argument, assume some violation took place.

You were paid for his misdeeds and avoided public charges. You were paid for your silence. At the time, it was "just another bigwig" who, form your point of view, should have paid for his misdeeds.

Now you see that he's a few steps away from being the President of the United States.

You risk having to pay back the money you received (years ago - meaning it's most likely gone) in order to let the country know what kind of man YOU encountered.

It doesn't matter if there's an R or D after the name. You think "D" gets a free pass? Ask Gary Hart what he thinks about that. Ask Anthony Weiner. Bill Clinton didn't exactly get a 'free pass', though he survived.