Tyler Cowen mentions Citizens United today.

For all the anecdotal evidence, it’s hard to show statistically that money has a large and systematic influence on political outcomes. That is partly because politicians cannot stray too far from public opinion. (In part, it is also because interest groups get their way on many issues by supplying an understaffed Congress with ideas and intellectual resources, not by running ads or making donations.) It is quite possible that the court’s decision won’t affect election results very much.