Former New York City mayor Michal Bloomberg. (AP Photo/John Minchillo)

Fox Business Network has shrunk the main stage to seven candidates for Thursday’s Republican presidential debate in North Charleston, S.C., and the fields in both major parties will continue to narrow until only two contenders — one Republican and one Democrat — meet in the general election debates this fall.

Or will they? In an interview set to air Jan. 24, the co-chairs of the Commission on Presidential Debates told  “The Open Mind” public television series that they are giving serious thought to the inclusion of a third-party candidate — something that hasn’t happened since 1992, when Ross Perot joined Republican President George H. W. Bush and Democratic nominee Bill Clinton onstage.

“The dynamic in the electorate right now and the dissatisfaction with the two major political parties could very conceivably allow an independent or a third-party candidate to emerge, and we are very clear that they would be welcome in these debates,” commission co-chair Michael McCurry told “Open Mind” host Alexander Heffner.

Heffner had observed that “it seems increasingly possible that a plausible debate stage would add a podium” this year and asked whether the debate commissioners “hope that there is another voice represented in the conversation.”

“I think it would be great,” said McCurry’s partner, Frank Fahrenkopf Jr. Neither co-chair said whether the inclusion of a third candidate would require any special accommodations or tweaks to what has been a one-on-one structure for two decades.

For now, there are no prominent third-party candidates vying to join the Republican and Democratic nominees, but that might be only because the major primaries haven’t played out. Current GOP front-runner Donald Trump has floated the idea of an independent bid if Republican voters pick one of his rivals of he feels hard done by the GOP establishment. Trump said in the most recent Republican debate that he would stand down in a primary defeat, but he has certainly changed his mind before.

Former senator Jim Webb of Virginia, who has already suspended his bid for the Democratic nomination, says he’s mulling an independent run. The New York Times reported over the weekend that former New York mayor Michael Bloomberg recently commissioned a poll to see how he might fare as an independent running against Trump and Democrat Hillary Clinton.

And can we rule out the idea that Sen. Bernie Sanders of Vermont — who calls himself an independent and socialist, anyway — would mount a third-party bid if he loses out on the Democratic nomination? He says he won’t, but the temptation could be pretty strong if Clinton beats him by a narrow margin and the campaign gets nasty.

What's more, a very polarized race between Trump and Sanders — or any race that includes Trump — could prove tempting for a would-be middle-ground candidate.

Qualifying for a general-election debate as an outsider wouldn’t be easy. A third-party candidate would have to be polling nationally at 15 percent, at least, to earn a spot onstage. That's a hard-and-fast number, too. The commission used to exercise some discretion — judging whether a candidate had a realistic chance to carry even a single state, for instance — but moved to a purely objective system in 2000, following the controversial exclusion of Perot during his second White House bid in 1996. (Commissioners determined that Perot was not a viable candidate that year, prompting the businessman to sue unsuccessfully for inclusion.)

Fahrenkopf told “The Open Mind” that the commission spent several months studying the fairness of its polling requirement — which also has been challenged — before deciding to keep it at 15 percent.

Still, it's easier in this cycle than in most to imagine an independent candidate reaching the 15 percent threshold. And with the debate commission sending such a welcoming message through the media, politicians who have been thinking about a third-party run might feel emboldened to try.

Heffner, in an interview with The Fix, said he left his conversation with McCurry and Fahrenkopf believing that they fully appreciate the significance of this “year of the outsider,” as he put it.

“I think they’re aware of the Trump revolution, or whatever you want to call it — the microphone that the media has provided for Trump,” Heffner said. “The two-party system, to many Americans, has disillusioned them to the point of questioning whether this is a democracy. And these men have a role to play in determining who is on that stage.”