A little fireplug of a man, moonfaced and brush-haired, the 40-year-old Gardner is so relentlessly upbeat it can be exhausting to spend time with him. He talks fast, in abbreviated clauses that don't always gel into complete sentences. His affect falls somewhere between a human ray of sunshine and an overcaffeinated hamster. When I interviewed him, he parried my questions with short, rapid-fire answers, anticipating each volley like a tennis player crouching behind the net.

Gardner, who is currently in the House of Representatives, readily admits his party has "overreached" in the past. He promises to be a pragmatist who focuses on kitchen-table issues. Democrats dismiss this as election-year posturing, but Gardner insists he's been consistent: As a state legislator, he notes, he advocated a renewable-energy bill over the Republican governor's veto; he has long been pushing his party for some sort of immigration reform (though he's slippery about what that involves); and last year, "a lot of nasty things were said about me in my own party about my unwillingness to demand the government shutdown," he says. Gardner acknowledges Obamacare isn't going anywhere as long as President Obama remains in office, and he says that if Republicans gain the Senate majority, "I'm going to be shouting from every desktop possible" in favor of an inclusive, bipartisan approach.

Gardner doesn't bring up any of the polarizing issues around which Udall has sought to frame the campaign, chiefly abortion. During this campaign, Gardner renounced his former support for the "personhood" initiative that will be on the Colorado ballot for the third time this year, saying he'd changed his mind after coming to understand the implications. But he remains a cosponsor of a federal personhood bill and has danced around aggressive questioning on the issue. (At one point, he even denied the federal personhood bill existed.) Frustratingly for Democrats, Gardner is a glib and talented politician, able to spit out non-answers with a cheery smile and without tripping up and saying something that could be used against him.

Democrats believe Gardner is just putting a happy face on the same old extremism. In 2012, they note, National Journal ranked Gardner the 10th most conservative member of the House. (In 2013, he was 98th.) Despite his talk about immigration reform in the abstract, they point out, he's voted to rescind DACA, Obama's executive action sparing some young illegal immigrants from deportation, and he doesn't support a path to citizenship. (When I pressed him on this, he said he was for "some kind of earned status," but as for citizenship, "I don't know that that is a universal demand by anybody.") While he claims he opposed the shutdown, he wasn't outspoken about ending it.

"The tactic of Democrats in Colorado has been to create a narrative about the Republican candidate six months before the election"—that they're in the pocket of Big Oil or a social-issues-obsessed ideologue—"and then opportunistically wait for the Republican to fulfill it," says Rob Witwer, a former GOP state legislator who's been close to Gardner since they came to the statehouse together. Past candidates like Tom Tancredo and Ken Buck always fit the bill. But "the narrative they created for Cory Gardner doesn't fit him. He hasn't behaved the way they said he would," Witwer says. "He's not the person they said he would be, and now, as voters see he's not that kind of person, it's become a credibility issue for Udall."