Is 'Hispanic" a racial category?

I always wondered where 'Hispanic' came to mean a racial category.  That it started with Richard Nixon and come to flower under Jimmy Carter I never would have guessed. 

From the LA Times, Judge Sotomayor, a mythic 'Hispanic'.

Jonathan Zimmerman thinks she should be judged on her merits as do all sane people and not because she's 'Hispanic'.

I put the term in quotation marks because it's a recent invention, dating to the 1970s and '80s. Before then, when Sotomayor was growing up with her Puerto Rican family in New York City, she was not Hispanic.
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All that would change in 1977, when the Office of Management and Budget instructed federal agencies to classify Americans as one of four races -- white, black, American Indian/Alaskan Native or Asian/Pacific Islander -- and also to distinguish between two ethnic categories, "of Hispanic origin" and "not of Hispanic origin." Since then, the census has asked people their race and whether they're Hispanic, which is not listed as a "race" per se.

Increasingly, however, Americans thought of it as such. Government agencies used "Hispanic" alongside "Asian" and "black," making Hispanic into a de facto racial category. Businesses and educational institutions counted Hispanics -- or, sometimes, "Latinos" -- as a race in diversity and affirmative action reports.

Not surprisingly, then, Hispanics became more likely over time to identify themselves as a separate race too. In the mid-1990s, 60% of the respondents to a study of more than 5,000 Latin American immigrants self-identified as "white," for example, but only 20% of their children did so.

That's an unprecedented development, as the United States had continuously absorbed people formerly identified in the census as from nonwhite races into the white majority. Jews, Italians and Slavs were all once classified as separate races; now, they're white. But Hispanics are moving in the opposite direction -- from white to nonwhite. In our minds, at least, they've become a minority race.