Sounds like a trumped up charge to me —
I doubt it was "trumped up." Blown out of proportion, certainly, but not "trumped up." This type of alleged crime almost necessitates a paper trail - person A gives money to persons B, C, D, E, etc., and those people then give money to campaign X. Each of these transactions leaves a paper trail - there's no way the USAO could have gotten an indictment without showing that paper trail.
This is most certainly a petty, vindictive prosecution, but I wouldn't go so far as to say "trumped up."