Interest groups now play a prominent role in the air war. Their collective investment in election campaigns has skyrocketed in the aftermath of Citizens United. Yet questions remain about whether interest group advertising affects the content of the specific issues being discussed. Do groups enter campaigns and engage voters on the same issues as their candidate allies? Or does the presence of more advertisers introduce competitive issue streams? This paper examines ad buys in Senate elections between 2008 and 2014 and the presidential elections of 2008 and 2012. A primary goal of the paper is to uncover the effect of high and low levels of "issue convergence" on election outcomes. Strategists often express concern that too many voices on behalf of a candidate can weaken the impact of ads. One might expect that as convergence between a candidate and his or her allies goes up (meaning the issue content of the ad buys overlaps across advertisers), the impact of ads on votes will increase. Ad effects should be weaker when a candidate's ads discuss different issues from allied groups and party committees. The results, however, suggest that high rates of issue convergence are only weakly related to election outcomes (and not always in consistent ways).
Franz, Michael M., "Interest group issue appeals: Evidence of issue convergence in senate and presidential elections, 2008-2014" (2000). Government Faculty Publications. 19.