In notes he made during his long post-presidency in Independence, Mo., Harry Truman was candid about the tricky nature of democracy. Yes, much of the nation’s fate lies in the hands of the president, Truman wrote, but the voters have the ultimate authority.

“The country has to awaken every now and then to the fact that the people are responsible for the government they get,” Truman observed. “And when they elect a man to the presidency who doesn’t take care of the job, they’ve got nobody to blame but themselves.”

The 33rd president’s words often come to mind as the reign of our 45th president unfolds amid tweet storms, raucous rallies and cries of “fake news.” For Donald Trump’s opponents, he is the embodiment of regression. For Trump’s supporters, he is nothing less than an American messiah.

My own view is that however ferocious the current hour feels, American history tells us that the people, when properly engaged in politics, have always managed to survive even the most divisive of presidents and the most depressing of eras. From Reconstruction to the first Red Scare under Woodrow Wilson, from the rise of a new Ku Klux Klan in the early 20th century to the cataclysm of the 1930s, from Joe McCarthy to the backlash against civil rights, our national story is no fairy tale. Despite the narcotic of nostalgia, troubled times are the rule, not the exception.

Every generation tends to think of itself as uniquely challenged and under siege. The questions of the present assume outsize and urgent importance, for they are, after all, the questions that shape and suffuse the lives of those living in the moment. Humankind seems to be forever coping with crisis. Strike the “seems”: Humankind is forever coping with crisis, or believes it is, and will until what William Faulkner described as “the last red and dying evening.” ...