When it comes to being a world leader, how old is too old? Voters in Malaysia had to ponder that question this week, as former prime minister Mahathir Mohamad led the country’s opposition alliance in an election to oust Najib Razak, the scandal-ridden incumbent prime minister.

At 92, Mahathir is almost three decades older than Najib. He has already been Malaysia's longest-serving prime minister, having held power from 1981 to 2003. But in the end, it didn’t seem to matter: Malaysia’s opposition won the election, its first victory in 60 years. Now, if Mahathir is sworn in (there is still some doubt about that), he will become the world’s oldest head of state or government.

As he arrived at a 3 a.m. news conference on Thursday, Mahathir seemed to joke about his age. “Yes, yes, I am still alive,” he told the waiting crowd.

Former prime minister Mahathir Mohamad and Wan Azizah, wife of former deputy prime minister Anwar Ibrahim, during an opposition meeting Jan. 7 in Shah Alam, Malaysia. (Huey May/AP)

It’s only when you include hereditary rulers and autocratic leaders that you realize that being the oldest world leader is a competitive title. Britain's Queen Elizabeth II, 91, holds the distinction of being the oldest world leader — a title she took from Zimbabwe’s Robert Mugabe when he was ousted from office last year at age 93. Beji Caid Essebsi, Tunisia's 91-year-old president, is the oldest serving elected world leader.

Mahathir’s decision earlier this year to run was a reflection of the state of Malaysian politics and, in particular, his public opposition to former ally Najib, who is linked to a multibillion-dollar financial scandal involving a state development fund. If seated, Mahathir is expected to use his power to pardon another major opposition figure, Anwar Ibrahim, who is serving five years on sodomy charges that his supporters say are politically motivated.

If he is pardoned, 70-year-old Anwar could run for prime minister — potentially succeeding Mahathir, a former-ally-turned-rival-turned-ally-again.

At the same time, however, the Malaysian election fits into a global conversation about how old world leaders should be. That debate was especially pronounced in the United States, where then-70-year-old Donald Trump faced off against 69-year-old Hillary Clinton in the 2016 election — the two oldest candidates in a U.S. presidential election, with the exception of incumbent Ronald Reagan in 1985.

Donald Trump and Hillary Clinton meet for their first debate of the 2016 campaign at Hofstra University in Hempstead, N.Y., on Sept. 26, 2016. (Melina Mara/The Washington Post)

Some opponents of Trump contend that the president’s age, in addition to a reportedly poor diet and limited exercise, have negatively affected his cognitive ability. This idea has become resurgent earlier this year amid accounts from the book “Fire and Fury,” by journalist Michael Wolff, that portray Trump as childish and unable to focus on the responsibilities of his office.

The White House has strongly pushed back against this idea, with Trump himself claiming to be a “very stable genius.” It has also criticized as “ridiculous” those who raised questions about a speech by the president last month in which he appeared to slur his words — although, as The Fix’s Aaron Blake noted at the time, Trump and his surrogates had repeatedly questioned Clinton’s health during the campaign.

There certainly are benefits to having older leaders in office — they can draw on wisdom accrued over decades of high-level decision-making, as well as the accompanying support and name recognition. But there’s no doubt that being a world leader also includes a workload and travel requirements that can be difficult for some older candidates to handle.

Looking globally, there have been a number of world leaders whose age appears to have affected their work. Before he was ousted, Mugabe was notorious for falling asleep during high-level meetings. When he was forced out of office last year, those leading the push said his “advanced age” meant he was no longer physically able to run the government.

In the United States, Reagan’s habit of forgetting things toward the end of his second term led to public speculation about whether his mental health was deteriorating. (After he left office, Reagan was diagnosed with Alzheimer’s, and his son later claimed that he had exhibited symptoms while he was president.)

Zimbabwe's Robert Mugabe appearing to be dozing during a state dinner with the Rwandan president in Bamako on Jan. 13, 2017. (Sebastien Tieussec/AFP)

However, legal age limits on heads of state or government are unusual. Instead, most countries tend to have some sort of minimum age requirement for running for office.

In many countries, this may be the same age as the voting age — 18 in many cases — although it can be higher. The U.S. Constitution requires presidential candidates to be at least 35. Even so, the world has seen a surge in younger leaders in recent years. France’s Emmanuel Macron entered office at 39, while North Korean leader Kim Jong Un is believed to be 34. The youngest world leader, Sebastian Kurz, was elected chancellor last year in Austria: At 31, he was just over one-third the age of Mahathir.

Indeed, the few limits there are can be strategically ignored — China's Xi Jinping, 63, is widely expected to flout Beijing's informal retirement age of 68 to continue for a third term — or outright repeal it, as happened in recent years in Turkmenistan and Uganda, by legal means.

That may be for the best. Experts generally agree that age alone can’t determine someone’s health or ability to work. Last year, Mahathir gave an interview to the Strait Times in which he explained that the secret to his youthful looks (the newspaper noted that his appearance had changed little in 12 years) was simple: Don’t overeat.

In March, Mahathir unexpectedly gate-crashed a forum where experts had been discussing whether he was too old to be leader. “There are two types of age. One in terms of years and another in terms of the body. The age of the body does not necessarily equate to the age in years,” he told the panel. “As far as health is concerned, I’m not senile yet.”

For Malaysian voters, the worry may have been not that Mahathir has changed too much, but that he has not changed enough. During his 22 years in office, Mahathir had a fearsome reputation as an authoritarian with little time for liberal values, and his tactics paved the way for Najib. And so far, Mahathir has expressed little regret.

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