Donald Trump's absence at Thursday's Republican presidential debate created a big opportunity for Sen. Ted Cruz of Texas — a big opportunity to fail, that is.

All the talk going in was that Cruz, running second nationally and in Iowa, would get more time to make his case for the White House before Monday's caucuses, while Trump held his rival event across town in Des Moines. True enough. But with the blustery billionaire missing from the debate stage, Cruz also became the de facto front-runner and faced what was clearly the toughest questioning from Fox News moderators.

He could have buckled under the pressure. He didn't.

In the biggest test yet of how he would handle the media scrutiny that comes with being the Republican standard-bearer -- and there was plenty of scrutiny from the moderators -- Cruz appeared ready for anything, especially challenges to his immigration record which have tripped him up before.

That's not to say he carried the first-place mantle with total grace. At one point, he complained to co-moderator Chris Wallace about the attention he was drawing.

"Chris, I would note that that the last four questions have been, 'Rand, please attack Ted. Marco, please attack Ted. Chris, please attack Ted. Jeb, please attack Ted," Cruz said.

The audience booed as Cruz aired his grievance, though it wasn't clear whether the response was aimed at the questioning or the griping. Perhaps it was some of both. Either way, the tea party darling seemed to sense the mood was souring and skillfully pivoted into a joke. After Wallace assured Cruz that the contrasts the moderators were trying to draw was part of debating, Cruz said this:

"Gosh, if you guys ask one more mean question, I may have to leave the stage," he said — an obvious jab at Trump's refusal to show up and take any questions at all. The crowd applauded.

Cruz did have a point, though. He was not only on the receiving end of pointed questions but also the subject of questions posed to other candidates — and not in a good way. Let’s review the four inquiries preceding the above Cruz response that got his dander up:

  • BRET BAIER: Senator [Rand] Paul, you are definitely not in the establishment category. But at the beginning of this campaign, you said you were your own man when asked about your father, former Texas congressman and three-time presidential candidate Ron Paul. Senator Cruz's campaign is out with a video saying that Cruz is the intellectual and political heir to your father's 2012 campaign and the liberty movement. And your father now says it's realistic that Donald Trump will be your party's nominee. So did you make a mistake by not fully — more fully embracing your father politically at the beginning of this campaign?
  • WALLACE: Senator Rubio, does Senator Cruz's record match his rhetoric?
  • WALLACE: Governor Christie, you have compared both Senators Cruz and Rubio to Barack Obama, saying that we cannot afford another inexperienced president. You've also said that Senator Cruz's vote to curtail the NSA surveillance program made America less safe. Is either of them ready to be commander-in-chief?
  • WALLACE: Governor Bush, here's the question — I'm going to ask Governor Bush the question. You criticized several candidates in this field on this stage for what you call unrealistic ideas about how to fight terrorists, including Rubio and Cruz, on the issue of their refusing to give the president authority to enforce the "red line in Syria." But, given the fact that your brother got us into two wars in Iraq and Afghanistan that have still not ended — that have still not ended — what lessons have you learned from his mistakes, sir?

Cruz’s memory is a bit off (these questions were not asked consecutively), but they were clustered closely together. The middle two were open invitations to bash Cruz. And while the first and last ones were ostensibly about Paul and his father, and Bush and his brother, they included references to Cruz that at minimum left ajar the door to criticism. Paul swung it wide open in his response; Bush chose not to walk through.

And here are some more very tough questions that were put to Cruz himself:

  • WALLACE: Senator Cruz, you talk tough about fighting terrorism. You talk about carpet bombing into oblivion. You talk about seeing if the sand will glow at night. But critics say that your record does not match up to that. You opposed giving President Obama authority to enforce his red line in Syria. Three years in a row now, you have voted against the Defense Authorization Act. How do you square your rhetoric with your record, sir?
  • This exchange with Megyn Kelly over Cruz's immigration record
  • WALLACE: Senator Cruz, you pride yourself on standing up to the D.C. cartel, but as we've seen to a certain degree tonight, there's a price for standing up to the D.C. cartel. Thirteen Republican senators have endorsed other candidates, none have endorsed you. ... The question is does your style sometimes get in the way of your ability to get things done, sir?

This comes with the territory. Trump has dealt with it in every debate that he’s actually attended — and complained about it plenty. In fact, his objection to tough questioning by Kelly in the first debate is a big reason why he didn't show up on Thursday.

[Sorry, Donald Trump. Megyn Kelly is a fantastic debate moderator.]

No one says you have to take your front-runner medicine with a smile. But you do have to take it, and if you want to hold on to your position, the side effect better not be a childish tantrum. (Unless your name is Donald J. Trump, in which case all rules of politics do not apply.) Cruz struck a more mature balance between pushing back and taking it in stride. If he’s going to pass Trump and carry the Republican banner, he’ll need to keep it up.