If he runs for president in 2020, Bernie Sanders would make Trump the youth candidate. Photo: Drew Angerer/Getty Images

Donald Trump is famously the oldest person to be elected to a first term as president. At the end of a hypothetical second term, he’d be 78, a year older than Ronald Reagan at the close of his presidency, and eight years older than the next oldest president, Dwight D. Eisenhower.

But if the idea of a 78-year-old President Trump seems weird, it’s worth remembering he’d be a year younger than a President Bernie Sanders would be upon taking the initial oath of office.

That’s worth pondering while reading Matt Yglesias’s new piece that credibly argues the junior senator from Vermont is the front-runner for the Democratic presidential nomination in 2020.

He’s doing exactly what a candidate who fell short needs to do to run a second time. He’s established a national political organization, he’s improved his ties with colleagues on Capitol Hill, he’s maintained a heavy presence in national media, and he’s traveling the country talking about issues.

In subtle ways he’s shifted his policy commitments to the center, making himself a more broadly acceptable figure in the party. At the same time, he’s held on to a couple of signature issues — Medicare-for-all and tuition-free public college — that give him exactly the kind of clear-cut and broadly accessible agenda that mainstream Democrats lack.

Yglesias goes on to explain that Sanders’s persistent role in the spotlight is partly attributable to the absence of a clear-cut successor as leader of his “movement.” Elizabeth Warren (who will herself be 71 in 2020) didn’t get off the fence and endorse Bernie in 2016, to the annoyance of many of his hard-core supporters. And the pol most People of the Bern seem to prefer, Nina Turner, is a former state legislator.

Still, there’s no getting around the fact that Bernie Sanders isn’t just old: he’d be the first octogenarian president halfway through his first term in office. Is the country ready for that? No one knows for sure (as Yglesias notes), but it’s an “issue” for Sanders that could be a genuine problem for some voters, while making Donald Trump the “youth candidate” at 74.

Yes, there have been a number of octogenarians who have served as leaders of other countries. But they are disconcertingly divided among tyrants (e.g., the current old-age champ, Zimbabwe’s 93-year-old Robert Mugabe, and Cuba’s 86-year-old Raúl Castro), figureheads (91-year-old Queen Elizabeth II) and larger-than-life post–World War II anomalies (Winston Churchill and West Germany’s Konrad Adenauer, known to his countrymen as “The Old Man”).

Among his biggest fans, Bernie Sanders is larger than life, and the youngest among them probably don’t distinguish much between octogenarians, septuagenarians, and the newly retired. With the continued aging of the baby-boom generation, old pols are also less anomalous than they used to be. Still, if he’s serious about 2020, Bernie may be testing the current genetic limits of political leadership. After two terms in office he’d be 87. Yes, there’s something fitting about a progressive leader fighting to preserve the New Deal legacy who actually remembers FDR, but it won’t be a shared memory for that many Americans too much longer.