Leveling the playing field: How campaign advertising can help non-dominant parties
研究竞选广告如何帮助非主导政党获得更多选票，利用墨西哥2007年媒体改革造成的广告分配差异，发现广告在信息不足和竞争不激烈的选区效果更显著。
We examine how campaign advertising affects electoral support. We propose a simple model where advertising disproportionately benefits non-dominant political parties, because voters are uncertain about and biased against such parties. We test this argument in Mexico, where one of the three main parties dominates in many localities. To identify the effects of exposure to campaign advertising, we exploit differences across neighboring precincts in campaign ad distribution. These differences originate from cross-state media coverage spillovers induced by a 2007 reform that equalized access to ad slots across all broadcast media. We find that, on average, ads on AM radio increase the vote shares of the PAN and the PRD, but not the previously hegemonic PRI. Consistent with our model, campaign advertising is most effective in poorly informed and politically uncompetitive electoral precincts, and against locally dominant parties of intermediate strength.