Mark Udall was elected to the Colorado House in 1996. He was elected to the U.S. House in 1998, defeating Republican Bob Greenlee with 50 percent of the vote to capture the seat vacated by the retirement of 12-year Democratic Rep. David Skaggs. He won re-election in 2000 with 55 percent of the vote.
He was re-elected in 2002 with 60 percent of the vote. He had only a token challenge in 2004 from Republican Stephen Hackman in the general election.