With Joe Biden‘s decision to drop out of the 2024 election, Donald Trump is now the oldest presidential nominee in history.

And voters are taking notice.

An exclusive poll conducted by J.L. Partners for DailyMail.com reveals that public confidence in the 78-year-old’s ability to do the nation’s top job is crashing.

Voters are now less confident that the former president can fully digest his national security briefings, hold his own in a meeting with Russian President Vladimir Putin or even survive a full four-year term than when we last asked them for their views in March.

With Biden out of the running, replaced by 59-year-old Kamala Harris, it suggests Trump can no longer deflect questions about rambling answers or muddled names by pointing at his 81-year-old rival.

For example, in March some 56 percent of respondents believed Trump could remember the names of key staff. (At that time the number for Biden was only 40 percent.) 

Now the proportion is 46 percent.

In the same way, where once 56 percent believed the former president could stay alert in the middle of a nuclear emergency. 

Now it is 49 percent, just four points higher than where Biden was.

Trump’s ability to do the job declined for each of the seven questions, by as much as nine points, in the view of voters.

It shows how the narrative has shifted with the sudden withdrawal of Biden. 

James Johnson, co-founder of J.L. Partners, said the issue should be a concern for the Trump campaign, although it had not yet reached the sort of level that could end his run. 

‘With Biden out of the race, the focus on age has moved onto Donald Trump. And voters do harbor some concerns about that, as our poll shows,’ he said.

‘There is, though, a big but. 

‘Unlike with Biden, those concerns never come up unprompted in focus groups. They are not top of mind and, remember this is a guy who was standing waving a defiant fist while covered in blood just a few weeks ago. 

‘That represents a lot of things, but infirmity isn’t one of them.’

Donald Trump is on the road this week, trying to define Kamala Harris in the view of voters. But his advanced age is also now under scrutiny without 81-year-old Joe Biden in the race

Biden passed the torch to Vice President Kamala Harris on Monday night in Chicago

Trump has endured a rough few weeks. Our poll also found that Harris had eaten into his overall poll lead, leaving him just two points ahead.

And the poll found that voters thought Trump’s age would be a good reason for voting for Harris. 

It ranked second of the possible attack line. ‘Donald Trump is too old to be president’ was rated one of the two most persuasive reasons to vote Harris by 35 percent of voters, while 22 percent ranked one of the least persuasive (a net rating of plus 13).

It was beaten only by the argument that Trump would bring more ‘division and chaos,’ which had a net rating of plus 18.

Even so, Trump allies believe age will not be a factor.

J.L. Partners polled 1001 likely voters from Aug 7 to 11, using a mix of online, landline, cell phone and in-app techniques. The results come with a margin of error of +/- 3.1 points

Talk show host and confidant John Fredericks said Trump was sharper than he had ever known him.

‘The Democrats have told us for two years it was not an issue and it didn’t matter,’ he said. 

‘Now, all of a sudden, they have a younger candidate and age matters? I mean, the hypocrisy behind what they do is beyond the pale. It’s really laughable. It’s clown show territory.’

The same poll also tested out Republican attack lines, to see which hurt Harris the most with voters. 

It found that attacks about her support for a bail fund, blamed for allowing the release of a man who went on to commit murder, could do most damage.