Jon Stewart is leaving the "Daily Show" at the end of the year. Stephen Colbert left the "Colbert Report" a few months ago to take over for David Letterman at CBS.

And as they head out the door, so do leading news sources for many of the youngest, most liberal Americans.

A 2012 poll from the Pew Research Center showed the two Comedy Central shows had some of the most liberal and youngest audiences in the media.

While 43 percent of adult "Report" viewers were between 18 and 29 years old, 39 percent of "Daily Show" viewers were. No other program or outlet tested had such a young audience.

Similarly, 43 percent of "Daily Show" viewers and 40 percent of "Report" viewers were liberals. Both ranked in the top five.

And fewer conservatives watched each program (14 percent of each's audience) than any show or outlet tested except MSNBC's "Rachel Maddow Show."

Of course, just because their audiences skew(ed) so young and liberal doesn't mean they are/were the leading source for young liberals.

But it's pretty evident they are/were up there. A survey for the Public Religion Research Institute and the Brookings Institution last year showed 17 percent of liberals said they trusted the "Daily Show" to give them the most accurate information. It ranked behind only the broad category of "broadcast news."

As for young people, the same poll showed 17 percent of 18-to-29-year olds cited the "Daily Show" as the most accurate, behind only CNN. A 2004 Pew poll showed they were already consuming comedy-show news about as much as broadcast news, a 2009 automated Rasmussen poll showed many young people thought programs like the "Daily Show" and the "Report" would replace regular news, and they've only grown in popularity since then.

Stewart has regularly dismissed the idea that his show is a real primary source of news for many young people. But as his tenure comes to an end, it's hard to under-estimate just how much it was.