Hillary Clinton swamped President Trump with substance-free attack ads during the 2016 election, while Trump ran far fewer, but more substantial ads, according to a new study of political advertising in the election.

The findings run counter to the narrative put forward by many Democrats that Trump was responsible for lowering the national discourse during the race.

Clinton vastly outspent Trump in the election, pouring $258 million into airing more than 400,000 ads during the race. Trump spent just $92 million and ran 120,000 ads. He ran fewer ads than even Clinton's Democratic primary rival, Vermont Sen. Bernie Sanders, who ran 128,000. Clinton's ads were far more negative in tone and content, according to a study conducted by professors of Wesleyan University, Washington State University and Bowdoin College for The Forum: A Journal of Applied Research in Contemporary Politics and published online on Feb. 22.

"The majority of the Clinton campaign's negative advertising attacked Trump's characteristics and personality. In other words, the attack ads were personal-focused as opposed to policy-focused. Fewer than 10 percent of ads attacking Trump focused on his policies, whereas about 90 percent was focused on Trump as an individual. Clinton's contrast ads were similarly devoid of policy discussion," the study found.

Trump's ads tended to be more substantial. Overall 70 percent of his ads focused on policy, compared with only 25 percent for Clinton's ads. The imbalance partly reflects Trump's novel strategy of not relying on paid advertising during the campaign, instead using media coverage to get his message out.

However, Clinton ran the fewest number of policy-oriented ads in the last five election cycles, the study found. Republican candidate Sen. John McCain had the next lowest number, 40 percent, in 2008. Nearly two-thirds of Clinton's ads attacked Trump on his personality rather than policy, by far the highest rate of any candidate since 2000.

"In stark contrast to any prior presidential cycle for which we have ... data, the Clinton campaign overwhelmingly chose to focus on Trump's personality and fitness for office (in a sense, doubling down on the news media's focus), leaving very little room for discussion in advertising of the reasons why Clinton herself was the better choice. Trump, on the other hand, provided explicit policy-based contrasts, highlighting his strengths and Clinton's weaknesses, a strategy that research suggests voters find helpful in decision-making," the study found.