DENVER -- Jared Polis and Walker Stapleton will square off in November in the race to replace Gov. John Hickenlooper after winning their respective primaries on Tuesday.
Polis won the Democratic primary early and will battle Stapleton, who won the Republican primary.
Colorado's last Republican governor was Bill Owens, who served from 1999 to 2007. Republicans hold four of the state's seven congressional seats and one of its two Senate seats.
Hickenlooper narrowly defeated former U.S. Rep. Bob Beauprez in his 2014 re-election bid by 4 percentage points.
The November race will feature debate over Colorado's rapid population growth and lack of investment in its infrastructure; the state's chronically underfunded public education system; and ensuring Colorado's rural eastern Plains and Western Slope aren't left behind in metropolitan Denver's economic boom.
The candidates also will clash over competing visions for health care.
Democrats want to extend coverage to include a public option; Republicans, emboldened by the federal repeal in the individual mandate that helps subsidize President Barack Obama's health care law, will fight expansion, especially when it comes to Medicaid.
Nearly one in four Coloradans is on Medicaid.
Polis is a tech entrepreneur, former state board of education member and founder of English-language schools for immigrants.
He has sparred with former state Treasurer Cary Kennedy over public education policy in the wake of teacher protests that gripped Colorado, Arizona and other states this spring.
All Democrats said they want to change the tax-and-spending amendment to confront Colorado's rapid population growth. All espoused universal health care, protecting public lands and promoting renewable energy.
Republican Secretary of State Wayne Williams said his office invested $900,000 in educating unaffiliated voters about their opportunity to vote.
Each received two ballots -- one Democrat, one Republican -- and, if they chose, could return just one of them by mail or at drop-off centers. Return both and they cancel out.
Kelly Kyle, a 40-year-old administrator for a food service company, slid her completed ballot into a downtown Denver drop box Tuesday.
She felt the crowded field of Democrats in the governor's race was similar and ultimately based her decision to vote for Kennedy on the endorsement of Emily's List, a political group that backs female Democratic candidates.
Kyle said she will support whoever wins the Democratic primary in November, but she wants to see "more progressive, pro-choice women" elected around the country.
"I definitely think it's advantageous to have more women in these positions to bring a different perspective," she said.
In suburban Denver's 6th Congressional District, two Democrats battled for the chance to unseat five-term Republican U.S. Rep. Mike Coffman.
Jason Crow, a former Army Ranger, beat out Levi Tillemann, a former adviser to the U.S. Energy Department during the Obama administration.
In El Paso County's 5th Congressional District, incumbent U.S. Rep. Doug Lamborn held off a Republican primary challenge from State Sen. Owen Hill and Darryl Glenn, a county commissioner.
The conservative district has elected Lamborn to six consecutive terms.AlertMe