Democrat Jared Polis, a five-term congressman, and Cary Kennedy, a former state treasurer, offer stands on schools, energy and public lands to the left of the centrist Democrat they want to succeed as Coloradans vote in primaries on Tuesday.
Republicans, meanwhile, hope to take a governor's office they haven't held since 2007, and Tuesday's GOP primary will select a challenger who offers a starkly different vision for purple-state Colorado that aligns with Washington's immigration crackdown and attempts to dismantle the Affordable Care Act.
The race to succeed two-term Gov. John Hickenlooper tops the midterm primary, one in which unaffiliated voters, the state's largest voting bloc, can participate without having to affiliate with one or the other of the major parties. A voter-passed 2016 initiative allows them to do so.
Hickenlooper has balanced oil and gas development with clean air standards, and as a former brew pub entrepreneur has overseen unprecedented economic growth in this rapidly-growing state of 5.6 million.
Republican Secretary of State Wayne Williams said his office invested $900,000 in educating unaffiliated voters about the change. 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.
"Citizens who make decisions here typically vote both Democrat and Republican. They're used to being able to pick a Democrat for one office and a Republican for another office," Williams said. "My goal has been to keep the disqualification rate as low as possible."
Republicans and Democrats offered starkly different post-Hickenlooper visions for Colorado's role — or resistance — in implementing Trump administration policies on immigration, the environment, taxes and health care.
Among the Democrats, Polis is a tech entrepreneur, former state board of education member and founder of English-language schools for immigrants. He has sparred with Kennedy over public education policy in the wake of teacher protests that gripped Colorado, Arizona and other states this spring.
Kennedy wrote a state constitutional amendment designed to increase public education funding and is endorsed by Colorado's largest teachers union. But a misleading attack ad on Polis and former state Sen. Mike Johnston, himself an educator, by a pro-Kennedy teachers' spending committee tapered the momentum of her grass-roots campaign.
Lt. Gov. Donna Lynne, a former health care executive, also is running. All agree that Colorado must change constitutional restrictions on taxation and spending to confront its rapid growth. All espouse universal health care, protecting public lands and promoting renewable energy.
The Republican candidates uniformly oppose any tampering with that amendment and embrace Trump's stands on immigration, tax cuts and promoting oil and gas — a $31 billion industry in Colorado. All differ with Trump on his trade policy, warning that tariffs and the initial stages of a global trade war will harm the state's economy.
Treasurer Walker Stapleton, a relation to President George W. Bush, has looked past the primary, criticizing Polis' $12 million investment in his campaign and his support for local control of fracking.
Victor Mitchell, a former state representative, portrays himself as an outsider, has invested nearly $5 million in his own campaign, and challenged Stapleton's truthfulness, especially his claim — since abandoned — to be the only U.S. state treasurer to endorse Trump's income tax cuts last fall.
Investment banker Doug Robinson, a nephew of former presidential nominee Mitt Romney, is a first-time candidate for public office. Rounding out the field is Greg Lopez, a former Parker mayor and regional director for the U.S. Small Business Administration.
In suburban Denver's 6th Congressional District, two Democrats are battling for the chance to unseat five-term Republican U.S. Rep. Mike Coffman. Jason Crow, a former Army Ranger, is the party favorite. Levi Tillemann, a former adviser to the U.S. Energy Department during the Obama administration, has tried to court anti-establishment forces on the left.
In El Paso County's 5th Congressional District, incumbent U.S. Rep. Doug Lamborn faces a Republican primary challenge from state Sen. Owen Hill and Darryl Glenn, an El Paso County commissioner who ran unsuccessfully for U.S. Senate in 2016. The conservative Colorado Springs district has elected Lamborn to six consecutive terms.