The case is Dallman v. Ritter (decided yesterday, by a 4-1 vote, with two Justices not participating). I’m afraid don’t have time to summarize the complex statutory scheme and the court’s complex reaction to that scheme, but the decision struck me as a pretty interesting and important, so I thought I’d pass it along.
For my general views of why many (though not all) restrictions on contributions to candidates are constitutional, even though restrictions on independent expenditures are not, see Why Buckley v. Valeo Is Mostly Right, 34 Ariz. St. L.J. 1095 (2003). But these views are largely not focused on the specific issues that Dallman discusses.