Sorry, but I don't buy the "But we couldn't have gotten single-payer" defense

[OilemFirchen]

137. Yes.

Starting with the Tillman Act of 1907 which stated:

All contributions by corporations to any political committee or for any political purpose should be forbidden by law; directors should not be permitted to use stockholders' money for such purposes; and, moreover, a prohibition of this kind would be, as far as it went, an effective method of stopping the evils aimed at in corrupt practices acts. Not only should both the National and the several State Legislatures forbid any officer of a corporation from using the money of the corporation in or about any election, but they should also forbid such use of money in connection with any legislation save by the employment of counsel in public manner for distinctly legal services.

... and the Federal Corrupt Practices Act of 1925. (And, subsequently, the Hatch Act of 1939 and the Taft-Hartley Act of 1947.)

However,

The campaign finance provisions of all of these laws were largely ignored, however, because none provided an institutional framework to administer their provisions effectively. The laws had other flaws as well. For example, spending limits applied only to committees active in two or more States. Further, candidates could avoid the spending limit and disclosure requirements altogether because a candidate who claimed to have no knowledge of spending on his behalf was not liable under the 1925 Act.

http://www.fec.gov/info/appfour.htm