On April 19, 1775, first at sunrise in Lexington and then at midmorning a few miles away at the North Bridge in Concord, the war for American independence began:

By the rude bridge that arched the flood, Their flag to April's breeze unfurled, Here once the embattled farmers stood, And fired the shot heard round the world.

Thus the essayist Ralph Waldo Emerson, turning to poetry to commemorate the day six decades later. A quarter-century on, Henry Wadsworth Longfellow could assume the events were still familiar to his readers:

You know the rest. In the books you have read How the British Regulars fired and fled,— How the farmers gave them ball for ball, From behind each fence and farmyard wall, Chasing the redcoats down the lane, Then crossing the fields to emerge again Under the trees at the turn of the road, And only pausing to fire and load.

Thanks in part to Emerson and Longfellow, generations of American children heard tell of the notable events of that day. We acknowledge some doubt, however, as to how many American children today know much of these battles, though they are still commemorated in Massachusetts as Patriots' Day. Yet when the Boston Marathon was the subject of a terrorist attack in 2013, the response was "Boston Strong," a kind of echo of the spirit of Emerson and Longfellow and of the farmers and silversmith they celebrated.

Unfortunately, for those of us unavoidably preoccupied by this year's Republican presidential race, the date of April 19 now brings to mind something else entirely: the smashing victory that day in the New York primary by Donald Trump, who won 60 percent of the popular vote and 89 of the 95 delegates at stake.

And so, sadly, if the New York primary turns out to be a key moment in the GOP nominating contest, and Trump goes on to win the nomination, the unfortunate image of a grinning con man, basking in the approbation of his credulous supporters will to some degree intrude on our remembrance of courageous and resourceful patriots.

This should not be allowed to happen. How can the Trumping of April 19 be prevented? It's simple: Let us see to it that New York on April 19, unlike Lexington and Concord, is not a harbinger of ultimate victory. Let us rather act so as to make New York on April 19 the high-water mark of Trump, more like the Battle of Rhode Island in August of 1778, an inconclusive British victory little remembered today because it was ultimately of little consequence. Such an outcome would be particularly appropriate because one knows that a Donald Trump of 1775 would have been a Loyalist—though he would have remained so only as long as the odds were with the British, and in the end would have done all he could do to curry favor with the winning side.

So opponents of Donald Trump need to take heart and succeed in their efforts to secure the very achievable goal of saving the Republican party from Trump.

Longfellow wrote "Paul Revere's Ride" in 1860, and it was published in January 1861, just after South Carolina had announced its intention to secede from the Union. Longfellow's effort to inspire a common patriotism did not deter the South from its foolish and destructive course. But this time, in the admittedly less dire circumstances in which we find ourselves, the hour is not too late. So let us proclaim a "cry of defiance, and not of fear" that "in the hour of darkness and peril and need" awakens our fellow Republicans to the "midnight message" of . . . Never Trump!