Jon Stewart and Stephen ColbertJon Stewart and Stephen Colbert are taking on causes more serious than a mock feud when they lead dueling political rallies on the National Mall later this month.

Stewart, host of Comedy Central's "The Daily Show," announced Monday on NPR that he will ask attendees at his Oct. 30 "Rally to Restore Sanity" to help restore the National Mall. The park and its memorials have a $400 million backlog of deferred maintenance.

On the event's website, Stewart wrote that ralliers should pick up after themselves, "in the name of sanity and reasonableness."

"We feel it's important to preserve this historic site for future rallies and for future Americans to rally on!" Stewart wrote. "But just in case you accidentally, like, put a beverage down on the Mall's coffee table without using a coaster, we figure that giving a little something back to the National Mall might, at least, soften the blow."

Colbert, host of "The Colbert Report," is asking attendees at his "Keep Fear Alive" march to donate to Donors Choose, which raises money for school supplies.