The demographic revolution of the past 50 years has transformed the United States from a predominantly white country into a truly multiracial nation. People of color have grown to 38 percent of the population today from 12 percent in 1966, and that metamorphosis paved the path to electing the first African-American president.

In November, Democrats have the chance to secure a decades-long electoral majority for decades, but they are at risk of missing this moment because too many consultants still stick to an outdated and ineffective campaign script that was written for a different, whiter era. Democratic spending is significantly misaligned with the pillars of the party’s electoral advantage, and campaigns throw away millions of dollars on ineffective ads while neglecting efforts to mobilize the rapidly growing ranks of minorities.

The evidence about the formula for Democratic victory at the national level is overwhelming. When large numbers of voters — particularly minorities — turn out, Democrats win. When turnout plummets — as it did in midterm elections in 2010 and 2014 — Democrats lose.

But the evidence has not translated to the actual practice of those who run and fund Democratic campaigns. The most critical decision campaigns have to make is how to allocate limited time and money between persuasion and mobilization. Persuasion is aimed at those people who have a history of voting regularly, and it generally takes the form of paid advertising, mainly on television. Mobilization involves the more labor-intensive work of turning out infrequent voters by making phone calls, knocking on doors and driving people to the polls.