With less than 40 days until the election, ProPublica has rebooted its Free the Files project in an effort to uncover who’s behind the hundreds of millions of dollars being spent on political TV ad buys, specifically in 33 swing markets across the U.S.

ProPublica senior engagement editor Amanda Zamora and reporter Justin Elliott join us on the podcast this week to explain how the app works, why we embarked on what has been called one of ProPublica’s “biggest and most advanced crowdsourced efforts ever done,” and how you can help us identify the outside groups influencing campaign 2012.

You can read more about the Free the Files project here, and help us unlock political ad spending on our rebooted (and quite addictive) news app. You can also listen to this podcast on iTunes and Stitcher.