Mr. Trump obliterated any chance that would happen by making the demonization of Mexican immigrants a centerpiece of a campaign that has catapulted white supremacy into the mainstream of American politics. He has also vilified Muslims and spoken ignorantly and contemptuously about African-Americans.

Latino grass-roots organizers hope that Mr. Trump’s nastiness will unlock the potential of the Latino electorate. That may well happen. They have made an ambitious push to get Hispanics to become naturalized citizens and to register to vote this year, particularly in swing states. The crush of applications for citizenship has overwhelmed the government.

In addition to defeating a bully, Latinos have plenty of reasons to enthusiastically support Mr. Trump’s main rival.

Mrs. Clinton has coherent, well-thought-out plans to address the matters that Latinos say they care about most. These include the economy, affordable access to health care, national security and education. Her record on immigration policy is not consistently progressive; as a senator in 2007, she opposed allowing unauthorized immigrants to get New York driver’s licenses. But she has changed her position on that issue and has promised to make the long overdue overhaul of America’s broken immigration system a priority. She also has vowed to continue, and expand, the program President Obama established to temporarily shield from deportation millions of unauthorized young immigrants with deep roots in the United States.

While immigration reform will no doubt entail a tough political fight, Latinos could make the prospect of an overhaul more likely by going to the polls in November. Low turnout among these voters would increase the likelihood of a Trump victory, which could mean mass deportations and more attacks on immigrants.

America’s 56 million Latinos — one third of whom are under 18 — are helping to shape America’s future in classrooms, workplaces and neighborhoods. It is only a matter of time before their mark on the nation’s politics matches their contributions in other spheres.

That moment should start now.