Former New York City Mayor and presidential hopeful Michael Bloomberg (D) celebrated his 78th birthday on Friday, emphasizing the increasing reality that the top tier of Democrat candidates is inching toward 80 years of age.

Bloomberg, born February 14, 1942, turned 78 on Friday. Now that recent national polls — as reflected in the RealClearPolitics average — show the billionaire in the top tier of Democrat candidates, one can officially say that three septuagenarians are the front-runners in the Democrat primary race.

Sen. Bernie Sanders (I-VT), who leads the field with an average of 23.6 percent support, will turn 79 in September and, if he scores the Democrat nomination and goes on to win the presidency, would turn 80 during his first year in office. Former Vice President Joe Biden (D), who is currently in second place with 19.2 percent support, will turn 78 later this year.

Age has been a factor and concern for some Democrats in choosing a candidate. The New York Times, for instance, refused to endorse Sanders for president, citing his age and health.

“Mr. Sanders would be 79 when he assumed office, and after an October heart attack, his health is a serious concern,” the board wrote.

Sanders has dismissed critics of his health and released letters from his doctors last year, who said that his heart muscle strength has improved and described him as “in good health currently.”

“At this point, I see no reason he cannot continue campaigning without limitation and, should he be elected, I am confident he has the mental and physical stamina to fully undertake the rigors of the presidency,” Sanders’ cardiologist, Dr. Martin LeWinter of the University of Vermont, stated.

Sanders has since defended his age, telling supporters on the campaign trail that there are “advantages to being old.”

“The ideas that I am fighting for now didn’t come to me yesterday,” he explained.

“I’ve been on more picket lines, I expect, than all my opponents combined over the last 30 years,” he added.

Biden’s mental stamina has also been a point of concern for Democrats, with mounting gaffes and lack of patience with potential voters on the campaign trail. He recently came under fire for calling a student a “lying, dog-faced pony soldier” — a remark the student took issue with, even though he made it in jest.

“It was kind of humiliating to be called a liar on national TV by the former vice president,” the student, Madison Moore, said. “Instead of answering that question straightforward, his immediate response was to attempt to invalidate me by exposing my inexperience.”

Nonetheless, the recent critiques toward Bloomberg center less around his age and more around his status as a billionaire, with some of his fellow contenders, including Sanders, accusing him of trying to “buy” the election.