American Crossroads Batting Average

At Mother Jones, Andy Kroll calculates win/loss ratios and concludes:

So there you have it. The US Chamber of Commerce and the Karl Rove-launched Crossroads GPS led the way, with .800 and .700 averages, respectively, in making the most of their (mostly) attack dollars. The labor group SEIU, meanwhile, finished last, albeit in an incredibly GOP-friendly election year. (Unlike the Chamber or many other outside groups, unions such as the SEIU do have to disclose most of their donors.) Most of these groups' funds, as you can tell, were focused on US Senate races around the country. And while the aforementioned conservative groups had plenty of success knocking off Democrats east of the Mississippi, their cash had far less influence out west, where Democratic incumbents Harry Reid, Michael Bennet, Barbara Boxer, and (probably) Patty Murray swatted away their challengers to eke out narrow wins on Election Day.