With the dawn of 2018, an especially tense election year revs up. Governors’ offices are up for grabs. Statehouses. And, oh yes, Congress. These midterms are when Democrats find out whether they can exploit Donald Trump’s apparent weakness to erase their party’s losses over the past eight years and erect a crucial legislative roadblock against his wild temper and worst ideas. They’re not just determined to turn the House or the Senate blue. They’re desperate.

And solidly purple Colorado is a fascinating arena to watch. Its delegation in the House of Representatives comprises four Republicans and three Democrats, but one of those Republicans, Mike Coffman, is acutely vulnerable and may in fact be the country’s best test case of whether a nimble G.O.P. incumbent in a swing district can survive an anti-Trump tide. He has been doing a delicate dance around the president: supportive one moment, censorious the next.

The Colorado governor’s race, meanwhile, is the country’s most interesting, bringing together an eclectic cast whose fates will speak volumes about what kind of candidate — young or old, male or female, entrepreneur or technocrat, affluent or not — voters want in the aftermath of Trump’s election. It will say just as much about how pragmatic the two parties are prepared to be.

Right now the probable Democratic front-runner is the gay multimillionaire, Jared Polis, 42, who is in his fifth term in Congress. He has better name recognition than his rivals, solid grades for his work on Capitol Hill and a history of tapping his own fortune to spend whatever it takes.

He’s also cunning. In one breath he told me, “President Trump is unpopular in our state, and voters certainly want a governor who’s going to be in the vanguard of the opposition.” That’s music to the left’s ears. In the next breath he emphasized his success in a “broad and diverse” congressional district that “ranges from small ranching communities to ski resorts.” He thus stretched himself into an elastic creature of the center.