President Joe Biden put the good of the United States, its citizens and people in the countries who look to this nation for leadership ahead of his own ambitions when he decided this week not to run for re-election.

The decision was clearly difficult. In the weeks since he struggled inarticulately through a debate with Donald Trump, the president resisted the perception that he is too old to run again. But once he was convinced that he might no longer pose the best chance to defeat Trump, he acted.

That makes Joe Biden an example of the kind of leader Americans should always seek as a president. It will add to his reputation as a commander-in-chief whose leadership transformed a nation that had been stalled by a pandemic and deep divisions.

On Sunday afternoon, almost six months to the day until the next inauguration, the 46th president gave his staff a one-minute warning. Before the news had time to leak, he announced on X, formerly Twitter, that he would not run again. He would devote himself instead to governing for the rest of his term.

President Biden’s unselfish action means the United States will not be inaugurating an 82-year-old in January, to the relief of many Americans. Polls have shown for months that voters of all inclinations doubted the president could carry the burdens of office until 2029.

But the question of age has not gone away with Joe Biden’s candidacy. Were Donald Trump to win a second term, he would take office as a 78-year-old who has exhibited his own signs of aging and consistently refused to release his medical records.

It is not age discrimination to bring up the capacity of a person in their eighth decade to remain mentally and physically fit for another four years. The office of the presidency is too critical to do otherwise. It was fair to question Biden’s future capabilities and it is equally essential to know the status of Donald Trump’s fitness.

Most important, this is not just any election. The distinctions between a Democrat and a Republican have gone beyond the legitimate policy differences that voters would normally use in making their decisions.

Candidate Trump has carelessly flung around threats that he will be a dictator for a day, that he will “go after” his opponents and use the Department of Justice for retribution. He has declined to say whether he would accept the results of the voting if it shows him as the loser. He admires bullies in high office and he considers any actions against himself to be “witch hunts.” He lies fluidly. He awaits sentencing for campaign-related felonies.

He is an old man who sees one more chance to get himself into an office he still won’t admit he failed to win in 2020. He is a danger to democracy.

So whether his new opponent is Vice President Kamala Harris or someone else emerges from the Democrats’ August nominating convention, Donald Trump needs to be confronted with a vigorous candidate and a rigorous contest.

As House Minority Leader Hakeem Jeffries said Monday, Joe Biden has been a “transformational” president. The fact that he had the humility to listen to family, supporters and donors about the wisdom of continuing may be the greatest act of transformation so far.

But there could be one more. The nation does not need another Jan. 6. It does not need fake electors and spurious lawsuits. President Biden can use the authority of his office to ensure that the 2024 elections are secure and untainted, and when the results come in, whether or not they are what Donald Trump was hoping for, the outgoing president can protect the legitimate transfer of power. Americans can trust Joe Biden to do that.

The Day editorial board meets with political, business and community leaders to formulate editorial viewpoints. It is composed of President and Publisher Timothy Dwyer, Executive Editor Izaskun E. Larraneta, Owen Poole, copy editor, and Lisa McGinley, retired deputy managing editor. The board operates independently from The Day newsroom.