Colorado's seven-member congressional delegation in the House of Representatives is made up of four Republicans and three Democrats, but only a couple of close races this year could tip that partisan balance.
Here is a rundown of the campaigns:
Congressional District (CD) 1
Active voters: Democrats, 210,897; Republicans, 82,290
Colorado's longest serving member of Congress, Democratic Rep. Diana DeGette has a built-in advantage in a district has elected only two Republicans - in upsets - since the Great Depression. DeGette, the House Democratic chief deputy whip, raised more than $1.1 million. Her Republican challenger, newcomer Casper Stockham raised less than $46,000, with $5,000 from beer scion Pete Coors and $6,450 from the Republican Party.
Boulder and Larimer counties
Active voters: Democrats, 176,870; Republicans, 138,923
Democratic incumbent Jared Polis' toughest challenger is Republican Nicholas Morse, of Fort Collins, in what's considered another safe Democratic district.
Polis, of Boulder, fought fracking and campaigned on increasing renewable energy, key issues in the district. Morse, a 30-year-old first-time candidate, told the website Vote Smart, "I don't support any regulation or government agency that restricts the development of natural energy on public land."
The Western Slope, southern Colorado
Republicans, 151,931; Democrats, 130,098
One of the two most competitive congressional races in Colorado, incumbent Republican Scott Tipton, of Cortez, hopes to hold off former state Sen. Gail Schwartz of Crested Butte in a race both national parties have invested in heavily.
The campaign has been fierce, focusing on public lands, jobs and energy development. The Cook Report, one of the leading election predictors, calls the seat "like Republican," meaning a Schwartz win would be an upset.
Republicans, 186,773; Democrats, 102,839
Republican Ken Buck, the former Weld County district attorney, has had an easy go of it in his first defense of the seat he inherited in 2014 when Cory Gardner won a U.S. Senate seat.
He holds a massive advantage in fundraising and name recognition over Democrat Bob Seay, the band and choir director at Lamar High School.
Republicans, 180,790; Democrats, 92,166
Incumbent Republican Doug Lamborn faces one of the most intriguing candidates anywhere in the nation, Misty Plowright, a Bernie Sanders Democrat and Army veteran who also is the first major party transsexual nominee for the U.S. House.
Still, this is the state's most Republican congressional district, and Lamborn is one of the most conservative members of Congress.
Eastern Denver metro area
Republicans, 138,584; Democrats, 138,105
Republican Mike Coffman has never lost a race in his 28-year political career. Democratic state Sen. Morgan Carroll could change that if Donald Trump's baggage on top of the ticket proves too heavy to bear in a district with almost as many Democrats as Republicans and laden with minorities and moderates.
Carroll has competitive financial backing and legislative name recognition, but so did former House Speaker Andrew Romanoff in 2014, and he lost by 9 percentage points.
Northwest Denver metro area
Democrats, 147,871; Republicans, 113,655
Many Democratic insiders peg incumbent Democrat Ed Perlmutter as a someday candidate for governor.
Republican challenger George Athanasopoulos is a strong Trump ally who, like the party's nominee, fears this year's election could be rigged.