Ray LaRaja has written this article for Political Behavior.  Here is the abstract:

This study assesses whether public disclosure of campaign contributions affects citizens’ willingness to give money to candidates. In the American states, campaign finance laws require disclosure of private information for contributors at relatively low thresholds ranging from $1 to $300. Drawing on social influence theory, the analysis suggests that citizens are sensitive to divulging private information, especially those who are surrounded by people with different political views. Using experimental data from the 2011 Cooperative Congressional Election Studies, it demonstrates how individuals refrain from making contributions or reduce their donations to avoid disclosing their identities.  The conclusion discusses the implications of transparency laws for political participation, especially for small donors.