Rep. Mark Udall (D) is up with another TV ad as he seeks to maintain his lead over ex-Rep. Bob Schaffer (R) in their battle to replace retiring Sen. Wayne Allard (R).

The 30-second spot, Udall’s second ad addressing national security issues, is set to run on broadcast and cable, with an initial buy in the Denver media market before expanding statewide. The Udall campaign described this latest ad as “a traffic change in our existing, open-ended buy.”

“It isn’t just something you see. Security is something you feel,” Udall says as the ad opens. “That’s why we’ve got to defeat al- Qaida where they’re based — in Afghanistan. And finally hunt down Osama bin Laden.”

Udall also touts his support for “adding an entire division to our military” and “a responsible plan to phase out of Iraq.”

Udall has been leading Schaffer in most polls taken on this race, although Colorado remains a majority Republican state.

— David M. Drucker