Which Donald Trump will show up at Thursday night's CNN Presidential Debate?

It's the biggest question surrounding Thursday night's CNN Presidential Debate, which is the first of two on-stage showdowns between President Biden and former President Trump in the 2024 election rematch.

Which version of the former president will show up at the primetime debate in Atlanta, the capital and largest city in the southeastern battleground of Georgia?

Will it be the undisciplined candidate who continuously interrupted Biden and debate moderator Chris Wallace dozens and dozens of times at their first debate in the 2020 election? 

Trump appeared to lose his cool, failed to condemn White supremacists, and his performance was widely panned by political pundits and viewers alike.

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The then-president reworked his strategy and his disciplined and measured performance in the second 2020 general election debate was a vast improvement. But it was too late, as Biden ended up winning the presidential election.

"If he replicates that performance, Donald Trump’s going to have a very good night," longtime Republican consultant and veteran debate coach Brett O'Donnell told Fox News.

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O'Donnell said his advice to Trump is "watch the second debate you had with Joe Biden in 2020 and replicate that performance. Watch it over and over and replicate that performance in this debate."

"He was measured but firm," O'Donnell said of Trump. "You can be aggressive and passionate without being offensive."

O'Donnell knows a bit about coaching presidential candidates ahead of their debates. He assisted in debate preparations for George W. Bush in 2004, GOP presidential nominee Sen. John McCain of Arizona in 2008 and Republican standard-bearer and then-former Massachusetts Gov. Mitt Romney in 2012. 

This election cycle, O'Donnell coached Florida Gov. Ron DeSantis ahead of his debate performances in the Republican presidential primaries.

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O'Donnell argues that Trump has been more disciplined in this race, saying that "for the most part, he’s been talking about the things that he needs to talk about. That’s the price of gas and groceries and the fact that people can’t afford their home or mortgage payments and can’t afford to buy their first house. Those are the kind of things that people want to hear answers to."

"Most Americans think that their personal world and the world in general is in chaos, and they’re looking for someone who’s going to restore order, and I don’t think that talking about personal issues helps either person," O'Donnell said of both Trump and Biden.

Along those lines, O'Donnell said Biden should avoid calling Trump a "convict," as the president has multiple times since Trump last month was convicted on all 34 felony counts in the first criminal trial in the nation's history of a former or current president.

"I think that’s a huge mistake. I think that plays into Trump’s strengths. First of all, I think the American people want this debate to be about their issues and not about the candidates’ issues.," O'Donnell said. "So if Joe Biden makes this about himself and Donald Trump, that only helps Donald Trump because it deflects away from the issues they should be talking about."

O'Donnell added that "highlighting this allows Donald Trump to talk about the justice system in a way that resonates with a lot of Americans. I think it’s a mistake."

He also warned against Trump focusing on Biden's age. At 81, Biden is the oldest president in American history and his health and mental fitness has been a major concern among voters, according to public opinion polling.

"I would let Joe Biden’s debating make that argument rather than Trump mentioning it directly," O'Donnell suggested. 

He predicted that "Biden is likely to be loaded with some clever line like Ronald Reagan had back in 1984" and that if "Trump does the job that he needs to do in the debate, I think that the age factor might be on display by itself without him provoking it."

Trump for weeks has ridiculed Biden as "weak, failed and incompetent" and said that the president "doesn't have a clue," as he's questioned whether the White House incumbent will be ready for the debate.

But on Tuesday, the Trump campaign attempted to recast Biden as a capable debater, with senior adviser Jason Miller telling reporters that the president "has been doing this successfully for 50 years." 

O'Donnell, who spoke with Fox News ahead of Tuesday's comments from Miller, cautioned the former president from "setting the bar low for Joe Biden."

"We should have high expectations for Joe Biden’s debate performance. After all, he’s the President of the United States," O'Donnell said. 

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O'Donnell said his advice for Biden "is be careful that you don't fall into the incumbent trap… Many if not most incumbents in their first debate, whether it’s Ronald Reagan or George H.W. Bush or George W. Bush or Barack Obama, most incumbents perform poorly in their first debate going for the second term."

"So the advice to Biden is avoid the incumbent trap because if he falls into it, it’s doubly bad because of all the age arguments," he added.

And O'Donnell emphasized that Biden has "got to somehow frame the race as a choice in defense of his record over the past four years. That is a tall order, but that’s something he has to do in order to justify picking him over Donald Trump."

"Neither of these candidates has really framed the race up yet for the American voter to understand how they should decide the race," O'Donnell argued. "And I think the debate is a perfect place for them to do that. And I think that Joe Biden needs to frame the race as a choice between him and Donald Trump. And Donald Trump needs to make this race a referendum on Joe Biden."

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