A supporter of Democratic presidential candidate Hillary Clinton attends a Democratic National Convention watch party in San Antonio on July 26. (Eric Gay/Associated Press)

Over the weekend, I wrote a piece breaking down Donald Trump's remarkably poor performance among Catholics. Some folks disagreed with the premise, arguing that there isn't really even a "Catholic vote" at all — that it's not homogeneous enough to consider it a voter bloc.

But every voter group has significant differences within it. And in fact, new data suggest that there's a little-publicized and rather large difference if you look closely at one of the most-discussed demographics of the 2016 election: Hispanics.

A Gallup poll shows that Hillary Clinton maintains a very big advantage among Hispanic voters — just as you might expect. Democrats, after all, have won this group by increasing margins in presidential elections, and that's a major GOP sore spot, given how quickly the U.S. Hispanic population is rising.

But the poll also shows that there is a significant split in the Hispanic community between Hispanic immigrants and U.S.-born Hispanics.

If you focus just on Hispanics born outside the United States, 87 percent have a favorable view of Clinton, while just 13 percent have a favorable view of Trump.

If you focus just on Hispanics born in the United States, though, it is much, much closer. Clinton's favorable rating drops to 43 percent, while Trump's jumps to 29 percent.

Those numbers, as Gallup notes, actually look a lot like how the country as a whole views both candidates:

Notably, U.S.-born Hispanics' views of the candidates are similar to those of the larger population of national adults. Forty-three percent of U.S.-born Hispanics and 44% of national adults view Clinton favorably. Twenty-nine percent of U.S.-born Hispanics view Trump favorably, while his favorability is 34% among national adults.

Therefore, Clinton owes a lot of her overall image advantage among Hispanics to those born outside the U.S.

The Pew Research Center last month broke this down in a slightly different — but equally telling — way. It compared Clinton's lead on Trump among Hispanics who are English-dominant with those who aren't.

While bilingual and Spanish speakers preferred Clinton in a head-to-head matchup by a massive 80 percent to 11 percent margin, English-dominant Hispanics were actually relatively evenly split, with 48 percent picking Clinton and 41 percent picking Trump.

The latter group's seven-point margin for Clinton looked, again, a lot like the rest of the country, which favored Clinton by a nine-point margin — 51 percent to 42 percent — in the same poll.

Indeed, if you look at these numbers, there doesn't seem to be a distinguishable "Hispanic vote" at all. The real difference-makers are Hispanic immigrants and those who don't speak English as their first language.

The good news for Clinton is that these groups are bigger than U.S.-born and English-first Hispanics. According to Pew, 57 percent of registered Hispanic voters are bilingual or Spanish-dominant.

It should be noted here that polling the Hispanic population is still a work in progress — in large part because of language and other barriers that often exist. And a February Washington Post-Univision poll showed U.S.-born and English-first Hispanics at the time were much friendlier to Clinton than the new Gallup and Pew data indicate. Back then, 61 percent of U.S.-born Hispanics liked Clinton, compared with 20 percent who liked Trump. Either these groups have soured on Clinton and warmed somewhat to Trump over the past six months, or we have conflicting poll results.

So we'll need to see more data. But the Pew and Gallup data suggest that our understanding of what constitutes the "Hispanic vote" to date might need some real updating.