Funny enough, the Left thinks exactly the same thing of the Right. They follow the rules, that the Right buys more politicians and are more likely to break the rules to get what they want.
As usual, the Left is wrong.
Neither party is pure as driven snow of course, but of major federal corruption convictions, Democrats win in a 60/40 landslide.
AND in terms of "being bought", of organized donors, say top 100, sorted by money, the top 1/3rd to top 1/4 of the list is all Democrat money, unions, trial lawyers and PAC's etc then a smattering of industries and .orgs that divide their donations roughly 50/50, before you get down to the first predominantly Republican only donors, the Koch bros. etc.
As to the abortive coup attempts, under FDR? Practically laudable, considering the extra-constitutional activities and attempted court packing to get a rubber stamp on them.
Granted, it's moral equivalency between a murderer and a thief, but any sane person picks the thief. Going all the way back to the roots of slavery and trason, it takes some stones to make any attempt to claim the GOP is more corrupt by any measure with a straight face.
And I say this as a Libertarian who despises both parties to one degree or another, for a variety of reasons.