DENVER -- Voters in three safe congressional districts are likely to choose who goes to Washington if they win their primary races on Tuesday.

The top races on Tuesday's ballot include an attempt to oust first-term Republican congressman Doug Lamborn, to replace Democratic Rep. Mark Udall and to find a conservative Republican to replace Tom Tancredo.

Voters in El Paso County will decide whether to keep state Rep. Douglas Bruce in the House or send him packing after he kicked a photographer in the House chambers on the day he was sworn in. Bruce is running against newcomer Mark Waller.

Lamborn has been fighting for his political life since he took office in Colorado's 5th Congressional District two years ago. Challenging him on Tuesday are Jeff Crank, a former aide to Joel Hefley, who held the seat for 20 years until retiring in 2006, and retired Air Force Maj. Gen. Bentley Rayburn.

Lamborn was forced to circulate petitions to get on the primary ballot for re-election instead of going through the GOP's El Paso County convention. Lamborn said he doubted whether county party officials could handle the convention; the county GOP defended its administration.

The first race was close for Lamborn, who won the 2006 nomination by fewer than 1,000 votes over Crank. Political observers say Crank has a better chance this year after Lamborn was criticized for failing to rein in spending in a district that is heavily Libertarian.

Four Republicans are fighting to succeed immigration firebrand and ex-presidential candidate Tom Tancredo in Colorado's 6th Congressional District, which spans the southern Denver suburbs.

Tancredo, a five-term representative, is stepping down.

Secretary of State Mike Coffman also was forced to petition onto the primary ballot after he said he was willing to give up his current office if he wins in November, giving Democratic Gov. Bill Ritter a chance to replace him with a Democrat.

Coffman faces two state senators, Ted Harvey and Steve Ward, and Wil Armstrong, a businessman and son of former U.S. Sen. Bill Armstrong, a powerful force in Colorado Republican politics who stepped down in 1990 after two terms.

In the 2nd District, Democrats Joan Fitz-Gerald, Jared Polis and Will Shafroth are fighting for the seat held by Udall, who is running for the U.S. Senate. Because the district, which includes Boulder, is heavily Democratic, the primary winner will likely win the general election in November.

Fitz-Gerald and Shafroth cried foul after Polis, who made his fortune as an Internet entrepreneur, poured a record $5.3 million of his own money into the race, more than his two opponents combined. Polis countered that his investment proves he isn't tied to special interests.

Shafroth, who is running on his record as an environmentalist, has aired television ads portraying Fitz-Gerald, the former state senate president, and Polis as two children in a backyard brawl. The former head of the Great Outdoors Colorado open space program argues Democrats should be fighting for what they believe in, not each other.

In the 1st Congressional District, Republicans Charles Crain and George Lilly are vying to take on six-term incumbent Denver Democrat Rep. Diana DeGette. The central Colorado district, which encompasses Denver, consistently votes Democratic by wide margins.

Political consultant Floyd Ciruli said the three districts were drawn by lawmakers to concentrate party affiliations, creating safe districts for Republicans and Democrats.

Ciruli said its reduces competition and excludes members of the other parties or unaffiliated voters to participate in choosing their representative. He said that allows narrow interests more control.

"Sometimes these are the candidates who least represent the whole party," Ciruli said.