A chump is a specific kind of
fool - specifically, someone who believes and supports the person who is making fun of them, making the foolishness that more foolish. It's one
thing to be called an idiot, but to be a chump, you have to call the person who is calling you an idiot a great person because you are so clueless you do not realize the person has called you an idiot (or taken advantage of you in some
way).
The
Republicans who talk about law and order and serving their
country are chumps for supporting Donald Trump, who loves their support while laughing hysterically behind their backs because they are such fools! Trump would never fight for his
country - that's a job for chumps!