In the Republican presidential race, it is becoming increasingly difficult to separate fact from farce.

In last weekend’s season-opener of “Saturday Night Live,” a fictitious Herman Cain explained to a fictitious Shepard Smith in a fictitious Fox News debate why his experience in the pizza business qualified him to be president.

“There is no better motto for the federal government than that of a pizza place,” said Kenan Thompson, playing Cain, adding, “It’s 4 o’clock in the morning and you’re high as a kite and the stuff in your fridge is weirding you out — if you order it, pizza will come. Pizza will come! Oh, pizza will most definitely come. And if you vote for me, America, I promise you that I will deliver.”

The next morning, the real Herman Cain was on the real Fox News with a real host, discussing the phony debate. “I think it’s great!” he said of the pizza skit. “I’m going to use that in my next debate: If you vote for me, America, I will deliver.”

It was a cheesy pitch from the “Hermanator,” but it apparently won the pizza guy the business of “Saturday Night Live” alumnus Dennis Miller. The comedian and radio host announced Monday that he’s endorsing Cain for the nomination. Miller suggested that Cain adopt a new slogan, “Cain versus Not Able,” as an alternative to the candidate’s existing slogan, “Cain versus more of the same.”

(Come on, Dennis: You Cain do better.)

In all likelihood, Miller was driven less by his successors at “SNL” than by Cain’s stunning performance in Saturday’s Florida straw poll, in which he won 37 percent — more than runners up Rick Perry and Mitt Romney combined. That’s just about opposite the result of national polling; a new CNN survey finds Perry and Romney with a combined 49 percent and Cain with only 7 percent.

Analysts have been puzzling over Cain’s pizazz in Florida. The Post’s Chris Cillizza and Aaron Blake asked if the results, following wins in other straw polls by Michele Bachmann, Ron Paul and Rick Santorum, mean “the end of straw polls.” They wrote: “Only the most conservative portion of the Republican base shows up at these events, skewing the results to the most ideological candidate, not the most electable one.”

Cillizza and Blake are correct: The straw polls are tilted by a small and unrepresentative sample of voters choosing the most ideological candidates. But it seems to me that makes the straw polls a close approximation of the Republican primary electorate.

There are 3 million people in Iowa, for example, of whom just more than 600,000 are registered Republicans. But the 2008 Iowa Republican caucus had 120,000 participants. Of those, 60 percent were self-described evangelicals or born-again Christians.

Essentially, that means the Iowa caucus is a straw poll. In fact, Iowa’s Ames straw poll this summer (the one Bachmann won) attracted 16,892 people — a decent chunk of the primary-day electorate.

The other early-voting states tend to have more primary voters, but that doesn’t change the possibility that the Republican presidential nominee could be determined by a few thousand Iowans who aren’t typical voters or even typical Republican voters.

Most political observers rely on national polls or, at best, statewide polls to gauge the sentiments of presidential primary voters. But because the number of people who participate in the primaries is so small, the true sentiments of that electorate (and the likelihood of people to vote) are often less predictable than polls can handle. And those sentiments tend to be volatile and fickle.

For that reason, it would be foolish to rule out any candidate — even the former Godfather’s Pizza chief executive, who makes no attempt to watch his mouth.

“Some people want to say I’m the none-of-the-above candidate,” he told the Daily Beast after his Florida win. “Some people want to say there’s still unhappiness with the field. That is bullfeathers!” The article noted that the candidate was drinking wine — in the morning. (In a different interview, Cain used another word that begins with “bull” but does not end with “feathers.”)

Cain’s wave may not last long, given the small and mercurial electorate (ask Bachmann about that), but he’s enjoying the accoutrements of a serious candidate while he has them.

On Monday, he’s scheduled to sit down with Donald Trump, following a pilgrimage taken by Rick Perry, Mitt Romney and Sarah Palin. He’ll then sit down Tuesday with former New York mayor Ed Koch. On Wednesday, his new book comes out. Later, comedian Miller will hold a fundraiser for Cain.

At this pace, Cain’s ultimate triumph — a guest-hosting gig on “SNL” — is just a matter of time.