Ad warfare between super PACs dominated the Republican primary season, with Mitt Romney, Newt Gingrich and Rick Santorum all leaning heavily on outside groups. But according to a new report from the Wesleyan Media Project, Ron Paul's still-active campaign has made far less use of super PACs than his GOP rivals.

Paul-supporting super PACs were responsible for only 8.8 percent of ads touting the candidate from January to March. That amount trailed by 10 percent the amount of super PAC ads backing President Barack Obama, who shunned super PACs entirely until February. It also was 50 percent less than super PAC-made ads for Romney. Ads supporting Paul (including ones from his campaign as well as super PACs) outnumbered all the ads supporting either Santorum and Gingrich, both of whom were considered far more serious candidates.

Paul-supporting super PACs tend to be smaller than their counterparts; the largest, Endorse Liberty, had raised just $3.6 million through the end of March. Peter Thiel, an original investor in Facebook and StumbleUpon, runs Endorse Liberty and steered its money toward Internet ads rather than TV spots. Santa Rita Super PAC, which raised less than $500,000, ran occasional TV spots for Paul.

While Paul is a major long shot to challenge Romney, he has quietly gained ground in the delegate count at the state level, fueling hopes for his supporters that they can nominate him from the floor of the Republican convention in Tampa, Fla.

His independence and the fact that he is the only challenger remaining may be considered a good omen by observers worried about the influence of super PACs on elections.