It is hard to imagine a candidate more unworthy to serve as president of the United States than Donald Trump. He has proved himself morally unfit for an office that asks its occupant to put the good of the nation above self-interest. He has proved himself temperamentally unfit for a role that requires the very qualities — wisdom, honesty, empathy, courage, restraint, humility, discipline — that he most lacks.

Those disqualifying characteristics are compounded by everything else that limits his ability to fulfill the duties of the president: his many criminal charges, his advancing age, his fundamental lack of interest in policy and his increasingly bizarre cast of associates.

This unequivocal, dispiriting truth — Donald Trump is not fit to be president — should be enough for any voter who cares about the health of our country and the stability of our democracy to deny him re-election.

For this reason, regardless of any political disagreements voters might have with her, Kamala Harris is the only patriotic choice for president.

Most presidential elections are, at their core, about two different visions of America that emerge from competing policies and principles. This one is about something more foundational. It is about whether we invite into the highest office in the land a man who has revealed, unmistakably, that he will degrade the values, defy the norms and dismantle the institutions that have made our country strong.

As a dedicated public servant who has demonstrated care, competence and an unwavering commitment to the Constitution, Ms. Harris stands alone in this race. She may not be the perfect candidate for every voter, especially those who are frustrated and angry about our government’s failures to fix what’s broken — from our immigration system to public schools to housing costs to gun violence. Yet we urge Americans to contrast Ms. Harris’s record with her opponent’s.