Silver’s post does include thoughtful points about the limited effectiveness of campaign spending beyond a certain threshold, and about the potential that Rove’s high-profile push could “backfire” by making insurgent candidates appear more sympathetic to right-wing media and hardline donors. Those points may hold up after a fuller analysis. And his note about the relative difficulty of working with data on outside spending is well-taken—for example, while reviewing Sunlight’s data this afternoon I found different values in different places for the amount Club for Growth had devoted to attacking David Dewhurst, the mainstream GOP candidate for a Texas Senate seat.
But if technical difficulties really made a full accounting infeasible, Silver’s post could have at least noted for readers the significant share of campaign spending unaccounted for in his analysis. The key principle is that outside spending has reshaped the campaign finance landscape, and it’s crucial for reporters and observers of money in politics to account for it as they inform the public about how elections are waged. Hopefully, Silver will find a way to include this information should he bring his formidable analytical skills to examining campaign finance in the future.