U.S. Rep. Carlos Curbelo’s quixotic mission to join the Congressional Hispanic Caucus went nowhere, but he provided a useful service. The Florida Republican’s quest laid bare what the ambiguous bureaucratic category of “Hispanic” is and is not.

Curbelo had been asking to join the all-Democratic caucus since January. Last week, they finally told him to take a hike. No matter how moderate he may vote, there was no room in the caucus for him. So why wouldn’t the Congressional Hispanic Caucus just welcome Curbelo? He’s a member of Congress and a Cuban-American, and therefore Hispanic, isn’t he?

It’s not that simple. From the beginning in the 1960s, when radical Chicano activists, federal career officials and the Ford Foundation began to strategize on how to synthetically create this now federally recognized group out many different ethnicities, it was clear that a definition of “Hispanic” would be hard to come by.

Was it Spanish speakers? People of mixed race? Would the term extend to people who had been here for generations? (Lest we forget, some of these families in the Southwest have been here since the 1500s.) How about somebody with a German last name? Or a blond-haired, blue-eyed guy, like the present coach of the Oakland Raiders, who happens to be surnamed Del Rio?

They embraced the vagueness because it helped their ends. According to University of California Berkeley sociologist Cristina Mora, “Ambiguity was important because it allowed stakeholders to bend the definition of Hispanic panethnicity and use the notion instrumentally, as a means to an end.”

Mora, a sympathizer of the creation of the ethnicity but whose book “Making Hispanics” nonetheless renders a pretty accurate rundown of the events back then, wrote, “Activists thus described hispanics as a disadvantaged and underrepresented minority group that stretched from coast to coast, a wide framing that best allowed them to procure grants from public and private institutions.”

The two words “disadvantaged” and “grants” are what it’s all about. During a 1969 congressional hearings concerning creation of President Nixon’s Cabinet Committee on Opportunities for Spanish Speaking People, Rep. Edward Roybal (D-Calif.), was asked who the “spanish speaking people” were. He answered that they would be those who had not “assimilated into the lifestream.”

Similarly, seven years later, when Congress passed a joint resolution on this issue, it stipulated that “a large number of Americans of Spanish origin or descent suffer from racial, social, economic and political discrimination” and thus the Census Bureau should “implement an affirmative action program” for them.

In my own book, “A Race for the Future,” I quote University of California Irvine sociologist Ruben Rumbaut as remarking that this was “the first and only law in U.S. history that defines a specific ethnic group.” At the time, nobody batted an eyelid. The effort from the start was to create a minority group out of Mexican-Americans, something rank and file Mexican-American themselves did not want, incidentally.

In Southwestern states, the Ford Foundation spent millions organizing them toward this end. But Leo Grebler, the University of California Los Angeles sociologist who went out in the field, wrote later that trying to convince this population that they were a minority caused “irritation among many who prefer to believe themselves indistinguishable white Americans.”

Once that work began, it also dawned on the coalition promoting this issue that the grants and the votes in Congress would not come if this was seen strictly as a Southwestern issue. Puerto Ricans were then added, and later the conservative Cuban-Americans, reluctantly, over the opposition of activists.

La Raza, created in 1968 by the Ford Foundation, soon took the leading role in pushing federal agencies to concoct the group category, and the census to ratify it. It had “found that it could best secure more resources from state and private grantmaking agencies if it could frame its constituency as a sizable national, rather than regional minority group.”

If you’re a conservative, however, accepting a status as a separate and disadvantaged minority group is likely not your thing. So, ergo, you’re not Hispanic. Yes, the Congressional Hispanic Caucus kicked Curbelo to the curb because he’s Republican, but that is symptom of this larger issue.

The socialist firebrand Dolores Huerta made that clear two years ago when she said conservative Sens. Marco Rubio of Florida and Ted Cruz of Texas were not Hispanic. Rather, she said, they were “sellouts” and “traitors” who were “turning their backs on the Latino community.” Last week, the Congressional Hispanic Caucus ratified Huerta’s ideologically-driven definition of “Hispanic.” And, so, Curbelo was told no.