At 6 p.m. tonight, September 12, ABC and Univision will air the third Democratic presidential debate, slated to take place at Texas Southern University's Health & PE Center in Houston. But nobody from Colorado will have a microphone.

Former governor John Hickenlooper abandoned his quest for the White House last month in order to enter the U.S. Senate race against imperiled Republican incumbent Cory Gardner. And U.S. Senator Michael Bennet wasn't invited, owing to his failure to meet the criteria for participation, a formula that includes polling data and number of unique donors. But he hasn't taken the hint, and is still officially in the race despite being left in the dust.

Should he hang up his track shoes? Absolutely — and there are plenty of reasons why.

Start with these ten.

1. The best scenario for a Bennet victory involves the death of every other candidate

At this writing, there are twenty Democrats aiming for the presidency, and Bennet is first by only one metric: the alphabet.

Half of the candidates failed to meet the threshold for tonight's debate, which will spotlight former veep Joe Biden, New Jersey Senator Cory Booker, South Bend, Indiana, Mayor Pete Buttigieg, ex-U.S. Housing secretary Julián Castro, California Senator Kamala Harris, Minnesota Senator Amy Klobuchar, former Texas rep Beto O'Rourke, Vermont Senator Bernie Sanders, Massachusetts Senator Elizabeth Warren and entrepreneur Andrew Yang. Mega-rich guy Tom Steyers has already qualified for the next debate, expected to take place on October 15 in Ohio, with Hawaii Representative Tulsi Gabbard insisting she's on the cusp of doing so.

That puts Bennet among the lower batch of candidates in the embarrassing lower tier — and it's not a good look for him to be among those bitching about the standards set for debate qualification. The New York Times, which noted that Bennet is "not particularly close to qualifying," quoted him as saying, "We’re rewarding celebrity candidates with millions of Twitter followers, billionaires who buy their way onto the debate stage and candidates who have been running for president for years. These rules have created exactly the wrong outcomes, and they will not help us beat Donald Trump."

Still, even New York City Mayor Bill de Blasio, among the loudest of the also-rans, admitted that it would be "tough to conceive" of remaining in the race if he didn't make the October debate stage. Unless all Bennet's rivals come down with the Andromeda Strain, the situation is the same for him.