What's the difference between a magician and a political pundit? The former lets you know when he's performing a trick; the latter never lets the viewer in on his deception. That's the premise of Merchants of Doubt, the eye-opening new documentary from Robert Kenner, the filmmaker who previously exposed the corporate-controlled food industry in his Oscar-nominated documentary, Food, Inc.

This time, Kenner takes on the secretive world of pundits for hire, or the group of TV talking heads who pose as scientific authorities while working on behalf of corporations that have their own investments at heart.

These illusionists were so charming that for decades, they were able to convince the media and legislators alike that cigarettes didn't pose a health risk, despite scientific evidence that proved just the opposite. Tobacco companies knew in the 1950s that smoking caused cancer, and by the 1960s that nicotine was addictive. Yet, 30 years later, the tobacco CEOs stood up before Congress and testified that nicotine was not addictive.

Of course, the same deception is also being used by pundits in an attempt to disprove climate change. Authors Naomi Oreskes and Erik M. Conway discovered as much when they compiled research to prove that only 2 percent of scientists who study climate change were skeptical about it. So why, then, did the media continue to present climate change as a debate?

The answer, as published in their 2010 exposé, also called Merchants of Doubt, is simple: Well-paid political pundits presenting themselves as experts are paid by the big oil and coal companies to refute the facts.

The two authors, along with countless scientists, experts, media figures, and even the unmasked pundits who shamelessly brag about their deception on camera, guide viewers on a journey to the heart of America's corporate trickery.

"The saying goes, ‘Once revealed, never concealed,’ " says Kenner. "But hopefully, once you see the way these guys work, you’ll start to recognize their tricks.”

Merchants of Doubt, which was produced by TakePart's parent company, Participant Media, rolls out in select cities on March 6 and nationwide on March 13. Get the latest updates at takepart.com/merchantsofdoubt.