Even among folks who think that there should be no limits on political spending, a sizable chunk of people support mandatory disclosure of who spends what on whom. There's even a bill working through Congress, the so-called DISCLOSE Act, "that would require non-profit political groups to reveal their funders." Candidates and political-action committees have to disclose donors, but there are a lot of other groups that don't.
The impulse to support mandatory disclosure makes a certain amount of intuitive sense but here are two things to keep in mind during any such discussion.
First, disclosure mandates will be used against politically weak individuals and groups. Consider a case from California in the 1990s, when two amateur activists - just the sort of citizen-types who are supposed to get involved in grassroots politics - tried to recall then-state Sen. David Roberti. Russ Howard and Steve Cicero didn't like Roberti's stance on gun control, spending, and other things, so they formed Californians Against Corruption and ran an effort to recall Roberti. The effort failed and the California's Fair Political Practices Commission (FPPC), headed by characters very mindful of Roberti's power, levied a fine of $808,000 against Howard and Cicero, whose campaign had spent slightly over $100,000. The cause of the fine was incomplete information on all donors who had given more than $100. It turned out that some donors didn't include all required information (such as their address, full name, employer, and whatnot). Such oversights might have been out of sloppiness or fear of reprisals (the information becomes public record), but the effect was to implicate Howard and Cicero in violation of disclosure rules. And get this, as Reason's Brian Doherty reported way back when:
The FPPC explicitly stated as an aggravating factor that Howard told a newspaper reporter that "the little guy can't participate [in politics] without running afoul of technical violations." In essence, the FPPC punished him in part for not agreeing with campaign finance law.
Second, anonymous political speech is at the very heart of the nation's founding and experience. For all the reverence show The Federalist Papers, which were authored by James Madison, Alexander Hamilton, and John Jay and are credited with helping to push ratification of the Constitution, commenters typically neglect that they were published pseudonymously, under the name Publius. There's nothing wrong with anonymous political speech that more speech can't fix. Voters discount anonymous claims if they are sketchy and undocumented, which is one reason why donors and groups who don't need to disclose their identities often do anyway. Another reason people voluntarily disclose is that public affiliation with a cause or a candidate is precisely the point of giving.
Watch ReasonTV's "Who is Publius?":