Mistakes were made.

When Congress passed the 1965 Hart-Celler immigration act, which President Lyndon Johnson signed 50 years ago this weekend, the law’s proponents sought to assure the public that nothing much would change in American society.

The legislation was hardly “revolutionary,” Johnson said. “It does not affect the lives of millions. It will not reshape the structure of our daily lives, or really add importantly to either our wealth or our power.”

Testifying before Congress, Attorney General Nicholas Katzenbach had said: “This bill is not designed to increase or accelerate the numbers of newcomers permitted to come to America. Indeed, this measure provides for an increase of only a small fraction in permissible immigration.”

Sen. Edward Kennedy said, “It will not upset the ethnic mix of our society.”

The nonwhite minority share of the population has more than doubled since 1965. Pew Research Center reports that between 1965 and 2015, new immigrants, their children and their grandchildren accounted for 55 percent of U.S. population growth. Pew projects that the white share of the population would be 13 percent higher today without the 1965 act. And, of course, the U.S. is on course for a nonwhite majority sometime in the middle of this century.

The changes wrought by the 1965 bill, which ended highly restrictive, race-based immigration quotas that had been in place since the early 1920s, were immense. The law opened up migration from Asia and Africa, and its emphasis on family reunification encouraged immigrants to bring a “chain” of family members behind them.

Princeton professor Douglas Massey argues that the 1965 act, which ended the Bracero Program of temporary work visas for Mexicans, also encouraged a lot of illegal immigration. “Probably most of the immigration from Mexico was caused by the 1965 Act, but in a perverse way most people don’t think of,” Massey said. “By cutting off avenues for legal entry in 1965, the Act produced mass undocumented migration, which set off a chain of events leading to border militarization, which backfired by promoting settlement rather than circulation.”

The recent decline in illegal immigration won’t much change the demographic picture. “The Latino population in the last decade or two has grown more from fertility than from immigration,” Brown University demographer John Logan said via email.

While the settled Hispanic population continues to expand, Pew projects that Asians will overtake Hispanics in the 21st century as the largest immigrant group. (“There is no danger whatsoever of an influx from the countries of Asia and Africa,” said Rep. Emanuel Celler, the 1965 bill’s House sponsor.)

Almost half of the U.S. population in the middle of this century will likely be immigrants or the descendants of immigrants who arrived after 1965, according to sociologist Christopher Jencks. (Brookings Institution demographer William Frey is less confident of that prediction, but agrees that it’s “possible.”)

To conservatives rallying around Donald Trump, the entire racial transformation of the nation must seem a dastardly sleight of hand. No president ever ran on a platform to change the U.S. majority from white to brown. No referendum was held.

Previous generations of conservatives sought answers to the questions “Who lost China?” and “Who lost Vietnam?” Since 2009, the conservative inquiry has focused on “Who lost America?” It’s a pointless and unsavory question, of course. But it does have an answer.

Francis Wilkinson is a Bloomberg View columnist. His email is fwilkinson1@bloomberg.net.