Verified answer

C is the answer. It use of the Commerce clause had allowed Congress to create monopolies in various industries, trucking, railroads, airlines, communication, et al. These monopolies garner tax breaks which allows these firms to make donations to those that give the breaks.

The Commerce clause was to prevent State Legislature from developing in-state monopolies (as was done under the Article of Confederation). But as Lord Acton once quipped, Power tends to corrupt and absolute power corrupts absolutely. Since FDR' threat to pack the Court, cases have been ruled to give Congress near absolute power. So far only J. Thomas has written opinions against this bad interpretation of that clause.

See links. I've link two of the most egregious cases where the then Supreme Court eviscerated both the concept of Federalism and the Founder's intent with the Commerce Clause.

C