The Gallup poll has been measuring public opinion on the subject of immigration since 1965, regularly asking respondents whether the flow of immigrants to the United States should “be kept at its present level, increased, or decreased.” Over the years the numbers have fluctuated greatly, but one finding has never changed: The percentage wanting less immigration always exceeded the percentage wanting more immigration.

Until this month.

On July 1, Gallup reported that for the first time, by a ratio of 34 percent to 28 percent, the share of Americans who favor more immigration surpassed that of those who want immigration reduced. (Another 36 percent support keeping immigration at its current level.)

The shift in opinion is being driven, like so much else in American life, by party affiliation. While Republicans’ views on immigration policy haven’t changed much over the past decade, pro-immigration sentiment among Democrats has soared. Since 2016, the proportion of Democrats supporting an increase in immigration has climbed from 30 percent to 50 percent, an all-time high. Among independents, the rise has been less steep, though still significant — from 23 percent to 34 percent. By contrast, just 13 percent of Republicans would like to see immigration grow.

It wasn’t always thus. There was a time, not long past, when the GOP was a stronghold of pro-immigrant sentiment and it was top Democrats who wanted more foreigners kept out.

During the 1980 presidential campaign, both Ronald Reagan and George H.W. Bush spoke feelingly in support of immigrants, refusing to demonize even those who entered the country illegally. “Rather than talking about putting up a fence,” Reagan urged, “why don’t we … open the border both ways?” As president, he signed legislation making millions of undocumented immigrants eligible for citizenship, and said he had always envisioned America as a land whose “doors were open to anyone with the will and the heart to get here.”

Bill Clinton, by contrast, pushed hard in the other direction. He supported laws that paved the way to mass deportations, and called for a crackdown at the border in language that today sounds almost Trumpian. The 1996 Democratic national platform condemned “criminal aliens” and faulted prior Republican administrations for having been so lax on undocumented immigration that “our borders might as well not have existed.”

Americans have always blown hot and cold on immigration. Still, the latest Gallup datum — that just 28 percent of Americans want immigration reduced — is striking. Never in the modern era has there been so little support for keeping would-be Americans out. The Trump administration’s persistent efforts to curtail immigration have, paradoxically, turned public opinion more pro-immigrant than it has been in decades.

Fittingly, Gallup’s finding came as the nation was gearing up to celebrate Independence Day. One of the reasons the 13 colonies rebelled against Great Britain was that the British government was impeding immigration to America. The Declaration of Independence denounced George III for “obstructing the Laws for Naturalization of Foreigners [and] refusing to pass others to encourage their migrations hither.” That was intolerable to the Founding Fathers, who welcomed newcomers from abroad and expected immigration to strengthen and enrich the new country. Of the Declaration’s 56 signers, in fact, eight were immigrants themselves.

“The United States was founded as an asylum and a refuge: a sanctuary. This was a form of patriotism,” writes Harvard historian Jill Lepore in her 2019 book, This America: The Case for the Nation. She quotes Thomas Paine, who called America “an asylum for mankind,” and Thomas Jefferson, who wanted the United States to be known as “a sanctuary for those whom the misrule of Europe may compel to seek happiness in other climes.”

When a failed uprising in the Netherlands sent thousands of Dutch refugees fleeing to America, George Washington wrote a letter to one of their leaders, Francis Van der Kemp, welcoming him and his fellow immigrants. It had always been his wish, declared Washington, “that this land might become a safe & agreeable Asylum to the virtuous & persecuted part of mankind, to whatever nation they might belong.” He hoped the newcomers would thrive, for then their “coming will be the harbinger for many more to adventure across the Atlantic.”

During the 1787 convention in Philadelphia that hammered out the Constitution, Pennsylvania delegate Gouverneur Morris drew considerable pushback when he proposed that no one be eligible to serve in the Senate without having been a citizen for at least 14 years. Oliver Ellsworth, later to become America’s chief justice, feared such a constraint would result in “discouraging meritorious aliens from emigrating to this country.” James Madison echoed that concern, and said restricting congressional eligibility to longtime citizens would “give a tincture of illiberality to the Constitution.” Benjamin Franklin pointed out that the desire of outsiders to immigrate to America should intensify Americans’ own “confidence and affection” in their nation.

What the 1787 debate revealed, observes David Bier of the Cato Institute, was that the founders didn’t just favor freedom of immigration, but also “opposed restrictions on citizenship that they felt would discourage immigrants from using that freedom.”

None of this is to suggest that America’s founders never had concerns about immigration. Then as now, there were complaints that newcomers weren’t assimilating, or were taking jobs from US natives. But the men and women of 1776 understood what a boon immigrants were, and — unlike George III — never sought to deter new Americans.

The strenuous efforts of the Trump administration to constrict immigration would have struck the Founding Fathers as perverse. But in the pro-immigration surge among the public at large, they would have recognized the echo of their own convictions, and rejoiced that, at least on this issue, the Spirit of ‘76 hasn’t faded.

(Jeff Jacoby is a columnist for The Boston Globe).