Trump says Biden is "not too old" to be president

• He's instead focused on Biden's "mental acuity," even as age has emerged as a top concern for voters ahead of 2024.

Driving the news: "Age is interesting because some people are very sharp and some people do lose it, but you lose it at 40 and 50, also," Trump said on SiriusXM's "The Megyn Kelly Show."

• "But no, he's not too old at all. He's grossly incompetent."
• Trump added that there are several world leaders who "were phenomenal in their 80s."
• "You know, there's great wisdom if you're not in a position like him. But if you go back 25 years, he wasn't the sharpest tack either," Trump said.

What they're saying: "President Biden has succeeded where Donald Trump failed at every turn, and that evidently isn't sitting well with the former president," Biden campaign spokesperson Ammar Moussa said in a statement.

• "President Biden's wisdom and experience has led to the most consequential presidency in decades, while Donald Trump continues to be haunted by his own historic failures."

The big picture: Biden, the oldest sitting president, would be 86 at the end of a second term, as his age has become a focal point among voters.

• 77% of adults think Biden, 80, is too old to effectively serve for four more years, with 89% of Republicans holding that view and 69% of Democrats, an AP-NORC poll out last month found.

• Just over half of all adults think that Trump is too old to effectively serve another term, with 71% of Democrats holding that view and 28% of Republicans.

Zoom out: Florida Gov. Ron DeSantis (R), 45, said this week during an interview with CBS Evening News that the ages of Trump and Biden are "absolutely a legitimate concern" for voters.

• Trump earlier this month slammed a Wall Street Journal poll that asked voters whether Trump's age was a concern. "Where did that come from?" he wrote on his Truth Social account.

Go deeper: America's aging leaders on display

Editor's note: This story has been updated with a statement from a spokesperson for President Biden's campaign.