Marco Rubio Sure to Face Heat at GOP Debate

MANCHESTER, N.H. — On the rise after his third-place finish at the Iowa caucuses, the stakes could not be higher for Marco Rubio during Saturday’s Republican debate.

After days of sustained attacks from GOP rivals Jeb Bush and Chris Christie, Rubio is expected to take fire from all directions.

Rubio said he’s ready, and is not preparing any differently.

"I know what I stand for," Rubio told NBC News Friday. "Preparing for debates is basically just staying current on the news and be prepared to answer in a serious way the questions that are asked of you."

Building momentum after his Iowa finish, Rubio has reserved his fiercest attacks this week for Hillary Clinton and Bernie Sanders, only delivering glancing blows to opponents like Donald Trump on the trail.

"I think Donald has an obligation to detail policies, and he hasn't done that on some of the key issues," Rubio said. "If he wants to be the nominee, he's going have to do that."

Related: What to Watch for in Saturday's New Hampshire GOP Debate

But his critics argue that it’s Rubio himself who has waffled on positions — most notably on immigration. He was behind the so-called "Gang of 8” bill in 2013 that his opponents deemed equivalent to amnesty for undocumented immigrants.

"I don’t believe immigration is a right or left issue," Rubio told NBC News. "We'll see what the American people are willing to support, but we're not going to ram anything down their throat and most certainly not going to do it by unconstitutional executive orders."

Rubio is likely to be hammered on the subject during Saturday’s debate — as well as questioned about his relative lack of executive experience.

Related: Poll: Trump Holds Lead in New Hampshire as Rubio Gains Ground

In his 2012 book, "An American Son," Rubio describes another debate that shaped him. He was working as a Miami surrogate for Bob Dole’s 1996 presidential campaign when a local Spanish-language radio station asked for a Dole supporter to debate a Democratic operative.

Rubio agreed to do it — and it did not go well.

"It was a valuable, if painful, lesson," Rubio wrote. "I vowed I would never again show up for an interview, speech or debate before I had done all I could to make certain I was the best-prepared person in the room."

Rubio's momentum — and his campaign — could hinge on how prepared he is this time around.