McCaskill joined Reps. Cathy McMorris Rogers, R-Wash., Tim Ryan, D-Ohio, and Steve Israel, D-N.Y., at the 11th annual Politics Online Conference in downtown D.C. to talk about how their offices are using Twitter, YouTube and other new media.

"It's not a fad, it's not a phase," McMorris Rogers said of the Web's growing influence. "It's a new way citizens are engaging elected officials. It's the new town hall. It's the new letters to the editors." McMorris Rogers, who is the vice chair of the House Republican Conference, is working to train GOP members to adopt new media for their offices.

But Twitter has drawbacks, too, the lawmakers emphasized. McCaskill, who has nearly 21,000 Twitter followers, said she needs to be cautious when working with colleagues on the Hill. "I don't want to be marginalized in the Senate by the fact that the people don't want to deal with me because interactions with me might immediately go on the public bulletin board," she said.