Brett O'Donnell, a top GOP political debate coach, said Wednesday that President Trump should be vigilant in his upcoming debate with Joe Biden, by steering clear of certain issues which might tank his White House reelection chances.

“One of the things that could derail the president is if he spends too much time on defense and not enough time on offense," O'Donnell told Fox News. "If he spends too much time talking about what went right and wrong with the coronavirus response – and instead talks about why this is China’s fault – [he will do well]. And [he should] say that a Biden administration would have handled it poorly, given how soft they are on China."

O'Donnell said Trump should also focus on the success being seen in the economy by way of promising jobs numbers and a stabilized stock market, despite the COVID-19 pandemic and recent unrest in major cities.

“That is one of his greatest arguments for why he should be reelected and it happens to be the thing that we’ll look at as the most important issue to vote on in an election," he said. "[Trump] has to defend what they’ve done on the economy. What could derail him is if he gets hung up on either side issues that folks don’t really care about, or defending specific actions during the pandemic.

When asked if Trump will -- or should -- go after Biden's mental faculties, O'Donnell said he expects the president to address the issue but doesn't think he will go into specifics.

MODERATOR CHRIS WALLACE SELECTS TOPICS FOR FIRST TRUMP-BIDEN PRESIDENTIAL DEBATE

"I do think the president will demonstrate that Biden has lost a step or two," he added. “Biden uses notes, teleprompters. He’s had staff who’ve had to help him… I don’t think Trump has to call him any names.”

Due to his long tenure in the Senate and his service as vice president under Barack Obama, O'Donnell claimed Biden will have a hard time dealing with Trump's attacks if the commander-in-chief is able to stay on message.

“The first time Biden attacks the president for being racist, the president can unload on him," he said. "There are all sorts of things the president can go after Joe Biden for, on almost every single issue. On China or trade, Trump can attack him for voting for the most favored nations clause, all of the bad trade deals, voting for NAFTA."

As for Biden's running mate Sen. Kamala Harris, D-Calif., the debate expert advised Trump to go after her and the other core Democratic party leaders as a unit and harp on the party's more progressive wing.

“The president should lump all of them together," he said. "Trump should attack Joe Biden, the socialist. It’s very apparent he wants to run from that label. The president should go after all of their ideas and not let Biden get away with separating himself from [party progressives]. He needs to attack them all as a group."

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The first debate, moderated by Fox News' Chris Wallace, is scheduled for Sept. 29 at Case Western University and the Cleveland Clinic in Cleveland, Ohio. The format will consist of six 15-minute-long segments – each one dedicated to a specific topic.

The nonpartisan Commission on Presidential Debates announced the issues Wallace has selected as topics on Tuesday, which will include the looming Supreme Court battle, the coronavirus pandemic response, the economy, and civil unrest in America's cities.