Fred Armisen Tells Letterman How He Does His Obama Impression (VIDEO)

Veteran "Saturday Night Live" cast member Fred Armisen has been impersonating President Obama since before the 2008 election and, if he stays on the show, could potentially do it for another four years.

On Tuesday night's "Late Show," Armisen sat down with David Letterman and revealed a few of his secrets to impersonating the President.

"Basically, when I do him, I just kind of make sure to kind of start up, I say, 'Hello!'" Armisen said in his best Obama. He also talks about Obama's other quirks, like his affinity for showing his profile and the way shakes his head slightly as if to say, "It's going to be okay."

Unlike his co-stars Kristen Wiig and Andy Samberg, who have left "Saturday Night Live" after spending a comparable amount of time on the cast, Armisen's impression gives him a reason to stick around through the fall. Similarly, Jason Sudeikis, who plays Joe Biden and Mitt Romney and has hinted that he will leave the show, but it is likely that he could return to do his impressions, a la Tina Fey doing Sarah Palin in 2008.

Then again, there's also Taran Killam and Jay Pharoah. Perhaps the torches will soon be passed?

Watch Armisen on Letterman above and check out the top 5 funniest Obama impressions below, via Gotcha Media