CNN reporter Jackie Kucinich said doubt around President Biden's mental sharpness will not go away after The Wall Street Journal reported that some lawmakers and other officials are concerned the chief executive has slowed down. 

"It's not going away," Kucinich said. "He's not going to age backwards."

"This isn't Benjamin Button here," she added, referencing the eponomyous 2008 movie character who ages in reverse. "This is Joe Biden."

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Former House Speaker Kevin McCarthy, one of the 45 people the Journal interviewed, provided his impression of Biden's mental ability. 

"I used to meet with him when he was vice president. I’d go to his house," he said. "He's not the same person."

Kucinich said it was clear Biden's advisers are concerned his age is an issue for his presidential campaign. She pointed to reports that the White House reached out to lawmakers to call the Journal back about their statements.

"You don't keep tabs on Democrats that The Wall Street Journal is interviewing and then have them circle back to highlight Biden's strength if … you don't think this is a vulnerability," Kucinich said. "All [the Biden campaign] can do is present him in as strong of a position as they can."

She also said the first debate between Biden and former President Trump, scheduled for June 27 on CNN, will be critical for convincing voters of Biden's mental fitness.

Biden, 81, is the oldest person to hold the presidency and has faced skepticism from voters and Republican lawmakers about his ability to do his job, especially as he battles Trump in the lead up to November. Many Republicans and even some Democrats, along with administration officials, said the president showed his age in private meetings, The Wall Street Journal reported.

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When meeting with congressional leaders in January to negotiate a deal to send additional funding to Ukraine, Biden spoke so softly at times that some people struggled to hear him, five people familiar with the meeting told The Wall Street Journal. He also relied on notes to make obvious points and paused and closed his eyes for extended periods.

The Biden campaign did not respond to a request for comment from Fox News Digital. 

Fox News' Landon Mion contributed to this report.