Campaign ad spending by outside groups has skyrocketed this presidential cycle due to the surging influence of so-called “super PACs,” a new study shows.

The Wesleyan Media Project examined ad spending in the 2008 and 2012 cycles, based on data provided by Kantar Media/CMAG. Among its findings:

-- Campaign ad spending by candidates has decreased from 97 percent of all ads aired during the first three weeks of January 2008 to 56 percent of all ads in the first three weeks of January 2012.

-- The share of ads run by outside groups has risen from about 3 percent of all ads during that period in January 2008 to 44 percent in the same period in January 2012.

-- Overall ad spending has gone down from about $50 million in the first three weeks of January 2008 to about $29 million in the first three weeks of January 2012.

Click here for the full report from the Wesleyan Media Project.

Worth keeping in mind as you examine the numbers: The figures don’t include ads run on local cable networks, and the cost estimates don’t reflect the steep increases in prices in the early primary states.

Also of note is the fact that the numbers for Florida run only through Jan. 25 – just a few days after former House speaker Newt Gingrich (R-Ga.) and the pro-Gingrich Winning Our Future super PAC went up on the air -- so the figures don’t give the most accurate read on ad spending ahead of the Sunshine State’s Jan. 31 primary.

See more on 2012 campaign spending at the Washington Post’s Mad Money tracker.

Staff writer T.W. Farnam contributed to this report.