Abstract
In 2010, the Supreme Court’s decision on Citizens United v. FEC, fueled public outcry about the growth of the cost of the political campaign and the influx of outside money in the form of independent expenditures. President Barack Obama seemed to agree with this speculation calling independent expenditures, “dark money” that “pulls our politics into the gutter” [Obama, Barack. 2015. “The Citizens United Decision was Wrong.” (Press Release). Retrieved from https://www.whitehouse.gov/the-press-office/2015/01/21/statement-president.]. Indeed, signs pointing to the increase in the cost of campaigns are correct, as 2014 saw the most expensive congressional elections in history. In this paper, we examine the effects of outside group spending on Senate races in 2010, 2012, and 2014. We find that outside group spending does play a significant, though small role in determining the vote share of a candidate. We also find that outside group spending in support of a candidate is generally more effective than outside group spending against a candidate, especially for the incumbent. Still, outside group expenditures pale in comparison to campaign expenditures for the challenger in terms of overall effect.