Quin, please do not mistake my silence on soft money as assent. I have not looked at that aspect as closely as the third-party issue ads. But since you have, how does BCRA's soft money ban not violate the First Amendment's prohibition on Congress making any law abridging the freedom of speech?
You seem to dismiss the free-speech concerns because BCRA did not completely constrain political speech. First, the Swifties were organized as a 527. BCRA did not apply to 527s. In contrast, 501(c)(4)s, such as Wisconsin Right to Life, whose as-applied challenge to BCRA will be heard by the Supreme Court on March 27, are not as successful in distributing their message. Not all speech will find other avenues. Second, how far is too far, in your opinion? How much political speech can Congress constrain before you think it violates the First Amendment?
The "sunshine consideration" is implausible because that idea is hardly new -- 527s are already required to disclose donors. If disclosure would satisfy McCain, why didn't BCRA stop there?