By Greg Giroux, CQ Staff

Freshman Colorado Rep. Doug Lamborn survived a challenge in his 5th District Republican primary election Tuesday, prevailing comfortably in a virtual rematch of the bitterly contested open-seat race he won in 2006.

Lamborn was the only challenged incumbent on a Colorado primary day that also produced strongly favored candidates to hold the state’s two open House seats for their respective parties.

Businessman Jared Polis — who spent heavily from his personal wealth — won a competitive Democratic primary in the 2nd District and enters the fall race with a big edge to succeed five-term Rep. Mark Udall , this year’s Democratic nominee for the U.S. Senate. Republican Mike Coffman, Colorado’s current secretary of state, won a comfortable primary victory in the heavily Republican 6th District and is highly likely to succeed five-term Rep. Tom Tancredo , the outspoken opponent of illegal immigration who briefly bid for this year’s Republican presidential nomination.

None of these districts is expected to produce a highly competitive general election contest, with CQ Politics rating all three as Safe for the incumbent party.

After its upcoming week in the center of the nation’s political universe as host of the Democratic National Convention in the state capital of Denver, Colorado will shift its spotlight to the state’s key matchups that were determined without primary competition.

Udall will face off against Republican former Rep. Bob Schaffer for the seat left open by retiring two-term Republican Sen. Wayne Allard . CQ Politics rates the race as Leans Democratic, in part because of a partisan trend that has seen the Democrats pick up the governor’s office, a Senate seat, two House seats and control of the state legislature over the past couple of election cycles.

In the normally Republican-leaning 4th District, three-term Republican Rep. Marilyn Musgrave , a narrow winner in 2006, faces a serious challenge from Betsy Markey, a former aide to Colorado Democratic Sen. Ken Salazar . CQ Politics rates this race in its highly competitive Leans Republican category.

Lamborn won the 5th District Republican contest with 46 percent of the vote, again defeating his two closest rivals from the 2006 primary: Jeff Crank, a former congressional aide and official with the area Chamber of Commerce, who took 29 percent, and Bentley Rayburn, a retired Air Force officer who received 25 percent.

The GOP primary in the heavily Republican district, located in a central portion of the state that includes Colorado Springs, was highly anticipated because of the closeness — and rancor — that marked the race two years ago. Lamborn, who positioned himself as the most conservative candidate in a crowded and conservative field, ran a hard-hitting campaign in 2006 that netted him a 27 percent to 25 percent win over Crank, as Rayburn took third with 17 percent. The campaign stirred such animosity that retiring 10-term Republican Rep. Joel Hefley, Crank’s former boss, declined to endorse Lamborn for the general election that he nonetheless won with 60 percent.

This time as the incumbent, Lamborn touted a conservative record that emphasized his opposition to tax increases and wasteful federal spending. Though he and Crank, his chief competitor, saw eye-to-eye on most policy issues, Lamborn drew strong support from the culturally conservative wing of the Republican Party while Crank had backing from many business-oriented Republicans.

The fact that Lamborn won Tuesday with a plurality rather than a majority suggests there still are many 5th District Republican voters who are not sold on him. But the opposition vote was too deeply split to allow either Crank or Rayburn to keep the race close. The two had initially brokered an agreement under which the candidate who was trailing in a specific poll would withdraw, but Rayburn objected to the implementation of a poll that favored Crank and remained in the race.

Colorado’s 5th is the most heavily Republican district in the state — President Bush took 66 percent of the its votes in 2004 — and Lamborn is a heavy favorite to win re-election against Democratic nominee Hal Bidlack, a retired Air Force officer who was unopposed in his party’s primary.

Lamborn is all but guaranteed to serve another term beginning next year in a Colorado congressional delegation that appears sure to include Democrat Polis and Republican Coffman as freshman members in January. The two well-known Colorado figures prevailed Tuesday in crowded primaries, carrying districts that also lean heavily to their respective parties.