There was a great deal of interest expressed at oral argument in the Citizens United case over the history of Congressional regulation of corporations. The Chief Justice made specific reference to Allison Hayward’s amicus brief during oral argument:

CHIEF JUSTICE ROBERTS: One of the amicus briefs, I’m not — maybe it’s professor Hayward, if I am getting that right — suggested the history of this 1947 provision was such that it really wasn’t enforced because people were concerned about the First Amendment interests and that the courts to the extent cases were brought did everything they could to avoid enforcing the limitations.

Seth Waxman also referred to the “sober minded Elihu Root,” reflecting the reference to Root in the McConnell opinion.
I’m no expert on this history, but I wondered if some of what is in the Hayward brief is contested, and if more light could be shed on the historical record. So I’ve invited a few historians of the era to weigh in with some thoughts. I am very pleased that Robert E. Mutch, one of the leading historians of this history, has agreed to weigh in with a guest post.
To ease readibility, I’ve posted his thoughts at this link. It is a fascinating read. His contribution begins:

Rick has asked me to comment on Allison Hayward’s amicus brief in Citizens United, in which she dissects the history of campaign finance law that Justice Frankfurter gave us in U.S. v U.A.W.
Allison is right to say that the history is flawed. It errs in getting historical facts wrong and in presenting a comforting, and misleading, vision of a politically unified Congress using calm reason to draft and amend campaign finance laws. Allison might also be right to say that the Court’s extensive reliance on U.A.W. has obscured acts of political opportunism that occurred in the writing of those laws. But I can’t go along with her when she says that the history of campaign finance regulation is one of partisans passing laws only as political weapons. The history of those laws is more complex and more interesting.