Chicago Mayor Rahm Emanuel (D) appeared Monday on "The Late Show with David Letterman," where he said Congress should back President Obama's call for military action against the Syrian government.

"I think the Congress of the United States should make sure America stands tall at this moment," Emanuel said.

"This is not an easy choice," he added.

He also discussed what it was like to be White House chief of staff -- and even did his best impression of former president Bill Clinton.