President Joe Biden addressed the elephant in the room — and in the presidential race — at the end of his election-year State of the Union address on Thursday.

Attempting a positive spin on voters’ concerns about his age, the country’s oldest-ever president leaned into his experience as a politician for over half a century.

“When you get to my age, certain things come clearer than ever,” Biden said before the combined chambers of Congress. “My lifetime has taught me to embrace freedom and democracy.”

But as Biden, age 81, and former President Donald Trump, 77, shift their focus to November’s general election, as the presumptive nominees of their respective parties after Super Tuesday, an even brighter spotlight will be placed on both men’s mental wherewithal.

And so far public opinion has not been kind, particularly to the current officeholder.

Americans have a dimmer view of Biden’s mental acuity than they do of Trump’s, according to a new Deseret News/HarrisX poll.

Almost two-thirds, 63%, of registered U.S. voters have doubts about Biden’s mental fitness for office, the poll found. Only 8% of Republicans and 30% of independents think Biden is mentally fit to serve as president of the United States, according to the poll, compared to 69% of Democrats.

Views on Trump’s cognitive agility are slightly more positive across the board.

About half, 51%, of Americans have doubts about Trump’s mental fitness as it relates to his ability to serve as president, the poll found.

Republicans are, unsurprisingly, less doubtful. The poll shows 79% of Republicans believe Trump is mentally fit to return to the White House, while 46% of independents and 22% of Democrats agree.

The poll was conducted by HarrisX among 1,007 registered U.S. voters from Feb. 26-27. It has a margin of error of +/- 3.1 percentage points.

While less than four years separate the former and current president, it’s common for individuals to experience aging in vastly different ways, according to Dr. Norman L. Foster, a geriatric neurologist and an expert on Alzheimer’s clinical and imaging research at the University of Utah.

“Characteristic of aging is that there becomes more diversity. So performance varies more broadly as we get older,” Foster said.

There are tradeoffs with getting older, Foster explained. Elderly individuals, on average, are less likely to act impulsively and make errors in their decision-making. But they are more likely to have decreased reaction time, the speed one can respond to a problem, and their injuries, including to the brain, become cumulative, building onto each other month after month.

Voters should consider each candidate individually, not just based on the number of years they’ve been alive, Foster said, cautioning that although growing tall in years might mean a decrease in sharp-mindedness and the ability to quickly recall details, it has also historically meant increased respect for one’s learned wisdom.

“In most societies ... individuals who have survived to a greater age are often revered or their opinions and guidance are sought,” Foster said. “There’s a reason that the sages are not 13-year-olds, they’re 70-year-olds.”

Poll: Most GOP voters say Trump reflects their values

However, Trump and Biden’s sagacity has been put to the test in recent months by the rigors of campaigning.

In February alone, Biden said he had just met with a former president of France who had died thirty years earlier, mixed up the Mexican and Egyptian presidents and was described in a special counsel’s report as a “well-meaning, elderly man with a poor memory” characterized by “diminished faculties in advancing age.”

The widely publicized release was written by special counsel Robert Hur, who was appointed by U.S. Attorney General Merrick B. Garland to determine whether charges were justified after classified files were found in Biden’s garage and former office.

Hur said charges should not be brought, arguing that Biden’s mental capacity was such that a jury would not convict him. Hur claimed Biden’s memory had declined dramatically over the last few years and that he was now unable to remember when he began and ended his term as vice president, the nature of his stance on Afghanistan, which had once been a central issue for him, and the year his son, Beau, died.

While Trump often makes a point of calling out his opponent’s gaffes, he has not been gaffe-free.

Trump recently confused his former primary challenger Nikki Haley with former House Speaker Nancy Pelosi, praised Hungary’s prime minister for his leadership of Turkey and claimed he defeated Barack Obama in 2016, not Hillary Clinton.

Despite a plethora of examples of both candidates missing the mark on questions a younger candidate may have answered with ease, Trump and Biden continue to feel the impact quite differently in the polls.

A New York Times poll published at the beginning of March found that 73% of all registered voters thought Biden was “too old to be effective.” Only 42% of voters said the same of Trump.

A Des Moines Register poll published on Tuesday found that 56% of Iowa adults thought Biden was too old to serve a second term. Only 22% said the same of Trump.

A Politico poll from February asked a similar question and found that 67% of voters said Biden’s age would prevent him from effectively serving another term, compared to 57% who said the same of Trump.

In the Deseret News poll, the No. 1 concern voters had about Biden getting reelected was “Biden’s mental acuity.” The same concern came in sixth place for Trump.

Biden’s annual health report was released on Feb. 28. The physician who conducted the physical, Dr. Kevin O’Connor, said, “President Biden is a healthy, active, robust 81-year-old male, who remains fit to successfully execute the duties of the Presidency, to include those as Chief Executive, Head of State and Commander in Chief.”

Biden is currently the oldest president in U.S. history. He would be 86 years old at the end of his second term if he is reelected. Trump would be 82.