Former Mayor Wellington Webb (search) on Monday turned aside Democratic pleas to challenge Republican Sen. Ben Nighthorse Campbell (search) next fall.

Chris Gates, chairman of the Colorado Democratic Party (search), said Webb is too busy working on his business interests,

"Obviously, I'm a bit disappointed because I think Mayor Webb would have been a high-powered addition to the race, but I completely understand his decision," Gates said.

On Friday, former Sen. Gary Hart (search) announced he would not challenge Campbell, 70, who is seeking his third term. Rep. Mark Udall has also decided against running.