Updated

If Donald Trump carries out his vow not to participate in Thursday night’s Republican debate on Fox News, occupying the middle of the stage of the Iowa Events Center in Des Moines will be two first-term U.S. senators and the children of Cuban-American fathers, Ted Cruz of Texas and Marco Rubio of Florida.

Trump has been highly criticized – by his opponents and political observers – for his decision to pull out of the debate because he claims Fox News Channel treats him unfairly in debates. Fox News executives say that the moderators are merely asking questions that a presidential candidate should address.

“[Trump's decision] is a very bad decision at a time when we’re having caucus in Iowa,” Alfonso Aguilar, a conservative Latino leader who is supporting former Florida Gov. Jeb Bush, told Fox News Latino.

Many believe Trump’s absence could most benefit his biggest rival, Cruz, with whom he is essentially neck-and-neck in polls of Iowa GOP voters. Cruz, who, like Rubio, who also is polling high in national polls, has in many Iowa GOP voter polls been in the top slot.

“It helps Cruz first and foremost. But it also helps everybody else, because it gives them more time and focuses the debate more on substance.”

Cruz and Trump have been locked in a back-and-forth race for first place in Iowa, which holds its first-in-the-nation caucus on Monday with Trump having jumped into the lead in the most recent polls.

Political scientist Cal Jillson, a professor at Southern Methodist University in Texas, suspects that Cruz may be more vulnerable to attacks by the others on stage anxious to bump up their standing.

“With Trump away, I think Cruz will be the target of Mike Huckabee, challenging him for the social conservative vote," Jillson told FNL, "and of the more mainstream candidates – Rubio, [Ohio Gov. John] Kasich, [N.J. Gov. Chris] Christie, and Bush – as too divisive to be electable."

"The others on the stage will be working to steepen his decline. Cruz is in a vulnerable position, more so, with Trump there to take some of the heat.”

Rubio has been indulging his impulse to go after Cruz in Iowa this week, questioning, among other things, Cruz’s choice of clients when he was a lawyer.

But he’s also taken shots at Trump, saying the bickering between the two – and the amount of coverage it has received – is getting out of hand.

“And I know all the press here is, 90 percent of their coverage is on this whole thing, ‘Oh, Donald Trump’s not going to show up, Ted Cruz is challenging him to a one-on-one, mano a mano debate,” Rubio said at a rally in West Des Moines, Iowa, according to The Hill. “Interesting sideshow. Greatest show on Earth…This is not a show — this is serious. We cannot lose this election.”

Trump and Cruz are running “outsider” campaigns, claiming that the mainstream Republican leadership is actively working against them. Although Rubio is running a distant third to Trump and Cruz in the polls, he is well ahead of Bush, Christie and the other more mainstream candidates.

Which also makes the Florida senator a potential target at the debate.

Super PACs backing Bush and Rubio have poured money into attack ads on each other. And the war of words between Christie and Rubio is amping up as well, with the New Jersey governor referring to Rubio as “a 44-year-old first-term senator who’s never accomplished anything,” according to the New York Times.

Christian Ucles, the Iowa political director for the League of United Latin American Citizens, or LULAC, told FNL that Trump’s absence, “is an opportunity for the GOP field to find their anti-Trump. Is this the moment Cruz or Rubio can become the anti-Trump?”