In my 2008 book, Choices and Changes: Interest Groups in the Electoral Process, I explored many different types of interest group electioneering in American politics, from PAC contributions and expenditures to party soft money contributions and issue advocacy. The book covered the period between roughly 1980 and 2004. 

In Chapter 6 of the book, I estimated models of outside group TV ads in House and Senate races between 2000 and 2004 (using data from the Wisconsin Advertising Project), looking for evidence that groups spend more in competitive elections, and that the draw of competitive elections is more prominent in cycles where control of the chamber was more at risk for the majority party.

The results of those models are below:

I remain very interested in this question, and we now have data on TV ad spending up through the 2020 election cycle, with the more recent data coming from the Wesleyan Media Project, which I co-direct. I updated my data from the book with these more recent cycles and ran new models identical in form to the ones above, with interactions (as blocked off above) for each cycle between 2000 and 2020. The coefficient estimates in House and Senate elections are graphed below.

Of course, much as has changed since the publication of the book, though in the direction suggested by the underlying thesis: permissive campaign finance rules and intense party polarization and competition should compel outside groups to spend aggressively in elections. Much is at stake in our current electoral climate and the guardrails preventing big money donors from investing in elections have been removed in recent years (most prominently from the Supreme Court’s Citizens United decision in 2010). We can see the influence of this in the graphs above, with competitive elections drawing greater amounts of outside group spending with each passing election. I’ll add the 2022 results to this graph after we finalize the data. And, of course, the 2024 election cycle is just kicking off…with lots of outside group election spending to come!