Former Colorado governor John Hickenlooper is getting out of the presidential race. His exit video was classy and responsible.

Judging from the video's tone and production value, I'd put good money on him running for Senate in Colorado. Recent polls show him clobbering Republican Sen. Cory Gardner in what would be a critical pickup for the Democrats.

Other presidential candidates should take note. Hickenlooper certainly wasn't a good candidate but he was far more plausible president than a slew of entrants, including former Maryland congressman John Delaney, Marianne Williamson, New York Mayor Bill de Blasio, and Reps. Tulsi Gabbard, D-Hawaii, and Tim Ryan, D-Ohio. And let's get real. The candidates who don't make the September debate — including officeholders such as Sen. Kristen Gillibrand, D-N.Y., Montana Gov. Steve Bullock, Washington Gov. Jay Inslee and Sen. Michael Bennet, D-Colo., many of whom I think would be equally if not better suited to the presidency than top-tier candidates — need to consider when and how to drop out.

Do they, as did Hickenlooper and Rep. Eric Swalwell, D-Calif., want to get out before they officially miss a debate, or do they want to be cut from the race and watch their donations and poll numbers sink to nothing? It's difficult to ask staff and donors to stick with you when your chances of surviving even to the first primary are so tiny.

Frankly, failure to make the September debate should be one — but not the only — threshold for excusing oneself from the race. If, by the end of the year, a candidate is not raising millions of dollars per quarter, is not in the top five or six places in any early-state poll, it's time to bow out. Perhaps they don't need to pull the plug this month, but by, say, Thanksgiving, they need to acknowledge reality.

Why? First and foremost, some of the other candidates could mount successful Senate races in winnable red states. Former HUD secretary Julián Castro in Texas and Bullock in Montana could put seats in play that otherwise would be out of reach. Second, we cannot stress enough that the smaller the field and the fewer people on the debate stage, the easier it will be for voters, staff members and donors to pick the most viable nominee. This is not a system set up to assuage the ego of candidates; it's designed to produce the nominee with the best chance to beat President Donald Trump.

Once the field gets down to serious and viable candidates (former vice president Joe Biden; Sens. Elizabeth Warren, D-Mass., Bernie Sanders, I-Vt., Kamala Harris, D-Calif., Amy Klobuchar, D-Minn., and Cory Booker, D-N.J.; South Bend, Indiana, Mayor Pete Buttigieg and former Texas congressman Beto O'Rourke), it will be possible for voters to compare and contrast. A voter who is super-progressive can decide whether Sanders or Warren is a better standard-bearer, or whether both are too risky and someone else is progressive "enough." A moderate voter can better assess whether Biden is sharp enough to take on Trump or whether Harris, Klobuchar, O'Rourke or Booker are ideologically palatable but have a better shot at beating Trump. Those fine distinctions are simply too difficult to make when 20 candidates are cluttering the stage over two nights.

Hickenlooper deserves praise, and a bunch of others deserve a strong shove off the stage.