https://phys.org/news/2018-10-unlimited-television-political-ads-votes.html

"We think political advertising is all-powerful, but it's not," Newell said. "Candidates who buy the most ads tend to get the most votes, but that could be drawing conclusions from coincidence. Those leading in the polls get more resources. So the additional advertising being purchased is essentially insurance and not as much to move the meter."

That is why Newell says it is unlikely the research will change how much campaigns spend on ads for the midterms or future elections. Given the high stakes, Newell says there is minimal risk of burnout as voters are still going to go to the polls. Commercial advertisers know reaching every viewer in a media market is not practical or cost effective, but political campaigns have nothing to lose.