As President Joe Biden celebrates his 81st birthday, his birthday will shine an uncomfortable spotlight on the fact that he is the oldest president in American history.

Biden jokes about it occasionally, and aides point to a busy schedule that would exhaust far younger individuals, but poll after poll reveals that the president's age is the most important concern for American voters.

PHOTO | COURTESY Joe Biden

That has been reinforced by a string of missteps, slips, and stumbles, ranging from losing his footing on the stairs of Air Force One to occasionally meandering responses during press conferences.

Despite a string of recent gaffes, former President Donald Trump, whom Biden is set to face next year, does not elicit the same level of fear among Americans despite his age of 77.

According to David Karol, a professor of government and politics at the University of Maryland, Biden is "not doing a lot wrong" but is battling to change perceptions about his age and other issues like the economy.

PHOTO | COURTESY Joe Biden

During a visit to speak with union members in Illinois, he quipped, "I know I only look like I'm 30, but I've been around for a long time" – and when a reporter tripped in the media area, Biden said, "I just want the press to know that wasn't me."

In other instances, Biden has used it to represent himself as a steady pair of hands in politics, claiming that age gives wisdom.

If re-elected, he will be nine years older than Ronald Reagan when he stood down at 77.

The White House has been skeptical of opinion polls, notwithstanding Democrats' recent election wins.

PHOTO | COURTESY Joe Biden

During a grueling election campaign, Biden's age will surely come under even more criticism.

Republicans have targeted Vice President Kamala Harris, who is only a heartbeat away from becoming President if the worst happens.

Harris broke ground as the first woman, Black person, and person of South Asian origin to serve as Vice President, but her approval ratings are as low as her boss's, at less than 40%.