Former Colorado Gov. John Hickenlooper will challenge Republican U.S. Sen. Cory Gardner in November, voters decided Tuesday night in the state's Democratic U.S. Senate primary.

Hickenlooper jumped out to an early lead over former state House Speaker Andrew Romanoff when initial results were posted shortly after the 7 p.m. deadline to return ballots in the all-mail election, and he never relinquished it. The Associated Press called the race for Hickenlooper at 7:37 p.m., when he led by 20 percentage points, according to the Colorado Secretary of State's Office.

"We must come together to reclaim our country and assert the fundamental decency of a nation that looks out for its people, treats everyone with respect and lives up to the ideals at the very foundation of who we are as a country," a jubilant Hickenlooper said in a live video feed after the race had been called.

"Let me be clear: Change is coming, and you and I are going to bring it together."

Recruited by national Democrats into a crowded primary last summer after he abandoned a stalled presidential run, Hickenlooper was the early favorite and the first candidate to make the primary ballot, by petition. But as ballots went out, he was met with weeks of blistering attacks from Romanoff, Gardner and national Republicans, who kicked off their summer ad campaign weeks earlier than originally scheduled after Hickenlooper was found to have violated a state gift ban.

"I’ve never lost an election in this state, and I don’t intend to lose this one," said Hickenlooper, who served two terms as Denver mayor and two terms as governor. "There’s far too much at stake. But this fight isn’t going to be easy."

With a nod toward the barrage of charges already hurled at him by Republicans, Hickenlooper said, "Donald Trump, the Republicans and their dark money groups are going to keep throwing everything they’ve got at us because they can’t defend Cory Gardner’s record."

Trump, who lost Colorado to Democrat Hillary Clinton by about 5 percentage points and has embraced Gardner, is underwater with state voters, according to polls. Hickenlooper left no doubt that he plans to run against both Republicans in the four months that remain in the campaign.

Hickenlooper said his opponents won't be able to defend Gardner's attempts to "gut people's health care" or his vote to cut taxes for corporations and the nation's wealthiest. "And they can’t defend Gardner’s cowardly silence as Donald Trump ignored a pandemic, fanned the flames of racism and divided the America we love."

Shortly before 8 p.m., Romanoff told supporters gathered online for a virtual primary night watch party that he had just called Hickenlooper to congratulate him and pledge his full support in the race against Gardner.

"I hope you'll join me," Romanoff said. "For all the differences we had, and there were many in this race, I am equally committed to making sure Cory Gardner is a one-term senator."

Romanoff, who has been in Ohio since traveling there a week ago to be with his ailing father, who died Sunday night, added: "I've learned this week that there are far more important things than losing an election."

As he encouraged his supporters to join Hickenlooper's campaign, Romanoff said, "The causes that we championed will go on — not with me in the U.S. Senate, but with other leaders who will take up the mantle. ... For you and for me, the work goes on."

As the conclusion of a primary season filled with curve balls neared, both candidates' campaigns were charging to the finish line as mail ballots poured in to county clerks, though vote totals fell short of the record primary turnout in Colorado's March 3 presidential primary.

The primary caps months of campaigning amid a pandemic — with the candidates pressing "enter" instead of pressing the flesh, in-person events replaced by virtual gatherings online and door knocks replaced by text message alerts.

Hickenlooper was the early front-runner and maintained an overwhelming lead in fundraising through the primary. But weeks of missteps and millions of dollars in attack ads could leave the still-popular former brewpub owner battered heading into a fall campaign that could determine which party controls the Senate after the election.

Romanoff, running against the establishment favorite from the left, hoped for an upset in a primary for a nomination he argued is too important to hand to a candidate with as many vulnerabilities as Hickenlooper.

Those include rulings this month by the state's Independent Ethics Commission that found Hickenlooper violated an ethics clause in the state constitution by accepting a private plane ride and ground transportation during trips he took as governor, as well as a contempt citation after he spurned a subpoena to testify in a virtual hearing.

True to form, the avowedly unpolished politico also found his foot frequently in contact with his mouth, including mangling an answer about the sentiment behind the Black Lives Matter movement and being forced to apologize for a years-old remark comparing busy politicians to whip-driven slaves.

Coupled with more pointed performances by Romanoff in a series of televised debates held after ballots went out to voters, those stumbles appeared to boost Romanoff's momentum, though the underdog still trailed by double digits in a pair of polls released in recent weeks, including one commissioned by Romanoff's own campaign.

Even as Colorado's electorate appears to be trending more liberal, however, Romanoff staked out positions far to the left, including support for the aggressive Green New Deal and the single-payer Medicare for all plan — potentially making him vulnerable in the general election in a state that still counts roughly equal numbers of Democrats and Republicans among its registered voters.

Hickenlooper will face a skilled and disciplined campaigner in Gardner — though he's one of only two Republicans still holding office statewide after a 2018 blue-wave election swept Democrats into offices they haven't held in decades.

"I think it's the record of results we can put forward for the people of Colorado," Gardner told Colorado Politics Tuesday night. "With John Hickenlooper it's a record of indecision and a lot of private jet trips."

Gardner said Hickenlooper still has to explain the ethics violations — when the Democrat accepted a ride on a private jet to attend a ceremony for a nuclear submarine named after the state and rode a limousine from the airport to an international conference in Italy.

Hickenlooper has said he thought he was complying with the ethics rules, but the ethics commission disagreed, handing him a record fine and the contempt citation earlier this month.

"He needs to give us more transparency on who he was on those jets with and whether those people had business before the state of Colorado," Gardner said.

Gardner said he also plans to press Hickenlooper to explain "his new, radical positions" on health care and the environment, though Gardner cited positions championed by Romanoff but rejected by Hickenlooper, such as Medicare for all and the Green New Deal. Indeed, much of Romanoff's campaign against Hickenlooper centered around his primary rival's opposition to those proposals.

"He needs to explain why 20% of the state tried to secede when he was governor," Gardner said, referring to a failed 2013 effort by some conservatives in 11 northeastern Colorado counties — representing 7% of Colorado's population — to form the 51st state.

The primary has seen an avalanche of outside spending, including $1.4 million spent by the National Republican Senatorial Committee on ads attacking Hickenlooper, $1.4 million spent by Let's Turn Colorado Blue, a shadowy group of Hickenlooper supporters, on ads attacking Romanoff, and nearly $2.7 million spent by the Senate Majority PAC, the leading Democratic Senate PAC, defending Hickenlooper.

After Hickenlooper was declared the primary's winner, a spokeswoman for the NRSC applauded the Democrats for nominating a candidate who said repeatedly during his presidential campaign that he wasn't cut out to be a senator.

"Over the next few months, voters are going to learn what Hickenlooper has been hiding — about his disregard for the law, his misuse of taxpayer funds, and all the illegal gifts and travel from his corporate sugar daddies. If watching him fall apart under pressure these last few weeks is any indication, 'hot mess' Hickenlooper is in for a very bumpy ride"," said Joanna Rodriguez, NRSC press secretary.

In a rare move, Gardner — who didn't face primary opposition — waded into the Democrats' election with an ad mocking Hickenlooper's frequent declarations last year on the presidential campaign trail that he wouldn't make a good senator.

There's a reason Republicans have spent so much money bashing Hickenlooper before he won the nomination. Recent polling has showed him leading Gardner by as much as 18 percentage points, and in April national election forecaster Nathan Gonzales at Inside Elections moved the seat from the "toss-up" category to "tilts Democratic," citing the state's shifting electorate and Hickenlooper's strengths as a challenger.

This story is from Colorado Politics, a statewide political and public policy news journal. Used by permission. For more, visit coloradopolitics.com.