In Colorado, Coffman and Miklosi Vie for Congress AURORA, Colo. - In his former, overwhelmingly Republican district, Representative Mike Coffman's remark that President Obama was "just not an American" might not have caused much of a stir. His aides note that registered independents in that deep-red territory were mainly those who considered Republicans too liberal. Now, because of a new Congressional map, Mr. Coffman, a two-term conservative with a long military résumé, finds himself in a Democratic-leaning district in the Denver suburbs in one of the most competitive House races in the country, with implications for the partisan split in the House as well as for the presidential race. And his comment last spring, which he quickly took back, does not play as well. "Most Coloradans don't want a member of Congress focusing on things like the birther issue," said Joe Miklosi, 42, the Democratic state representative trying to unseat Mr. Coffman. I think that is when people started taking a second look at Coffman. The comment by Mr. Coffman, 57, a push-up enthusiast known for suddenly dropping and doing a share of his daily 500, might have put him on the radar of Democrats and their allied groups looking for vulnerable Republicans to pick off. Until he spoke up on the president's background at a fund-raiser, Mr. Coffman was something of a nondescript figure in the House, known as a rare Republican member of the Armed Services Committee willing to entertain Pentagon cuts. He was not seen as an outspoken member of the far right. But the comment energized the campaign of Mr. Miklosi, who suddenly found himself on television denouncing his opponent. And it helped turn the race for Colorado's Sixth Congressional District - one of three seriously contested House races in this battleground state - into a magnet for outside money from national parties and advocacy groups. "It is a different ballgame," acknowledged Mr. Coffman, who was between phone calls to voters from his campaign office just outside Denver. It is clearly a competitive district, and it is a big transition. To cut into the Republican majority in the House, Democrats must win races like this one in the suburbs south and east of Denver, a district redrawn to the party's advantage, with Aurora serving as its heart and population center. If Mr. Obama hopes to carry the state, it is also crucial that he perform well here in Arapahoe County, a top target of the White House. Mr. Miklosi hopes to benefit from the extensive turnout operation the Obama campaign is mounting, with four field offices in the district. "It is a huge impact," Mr. Miklosi said. He moved to the district to run for Congress, but he is citing his history of working in the area through a nonprofit organization that distributes donated medical supplies, and noting his social ties to the community. As in the presidential campaign, Democrats are trying to appeal to women in the district and see them as the key to the election. The Democratic Congressional Campaign Committee has invested more than $2 million in the race, attacking Mr. Coffman for supporting limits on contraception, a plan to convert Medicare into a voucher program, and proposals that prohibit exceptions for abortion in the cases of rape and incest. Mr. Coffman and the National Republican Congressional Committee, which has also spent $2 million on its candidate, have fought back hard, faulting Mr. Miklosi for votes in the state legislature that raised taxes and fees and for his support for Mr. Obama's health care law. Mr. Coffman put out an ad accusing Mr. Miklosi of opposing some mandatory minimum sentences for sexual offenders, a claim the Democrat called badly distorted. Mr. Coffman, who waltzed to re-election in 2010, grew up in Aurora and points to his deep ties to a community that he remembers as a small, military-oriented town. He said his own career in the military and a tour in Iraq as a Marine civil affairs officer helped him relate to the district's many veterans. Most Democrats in the district are not members of the most progressive element of the party, he said. "It is a different Democrat, really blue-collar, working-class Democrats," he said, suggesting that differences on social issues would not decide the race. Mr. Coffman has also sought to emphasize his willingness to break with his party. He said that his experience in Iraq had left him opposed to the nation-building exercise the Bush administration pursued there and that his advocacy of Pentagon cuts had put him at odds with fellow House Republicans. "People see me as conservative in some areas, independent in other areas," he said. I think Democrats look at that. Mr. Miklosi has sought to turn the Pentagon spending issue around on his opponent, saying Mr. Coffman's inability to help House Republicans find a consensus on overall deficit reduction has led to the threat of automatic spending cuts and the prospect of layoffs at Buckley Air Force Base and other local installations. "He didn't get the job done, and as a result our generals and our admirals are handcuffed and we are not making defense cuts in a strategic way," Mr. Miklosi said. He said that Colorado was in a position to be a major player in alternative energy sources like wind and solar and that Mr. Coffman was too tied to traditional oil and gas development. In reviewing the race, the newspaper The Aurora Sentinel said both men were solid options for a growing city that would for the first time be in a single unified House district. But in endorsing Mr. Miklosi, the newspaper's editorial page said the increasingly diverse community had moved on while Mr. Coffman had not. The election next Tuesday will show whether voters see it that way as well.