No, not really triangulation. The Dems were (and still are) controlled by unions. Unions, back then, hated Illegals as it undercut their workplace demands, so the Dems were generally against Illegal immigration.
But then Bush took over, a man who always had a BIG SOFT SPOT for people that speak Spanish (as he did too). The Housing Bubble was in full force, and Illegals came by the millions to build those houses. At that point BIG MONEY (i.e. Republican Donors) determined that they needed the immigrants (legal or not, they didn’t care) to keep the gravy train going. One of the biggest of those was Bob Perry, of Perry Homes, based in Texas, who showered the Republicans with money, particularly in Texas (biggest donor in Texas but stayed under the radar as much as possible). So it was no surprise that the Republicans then supported immigration BIG TIME, and Amnesty to lock those workers in. There was no politics on the Republican side, just campaign donations based on economic interests - they would have been fine with a guest worker program.
Then Obama takes over. At this point, the Unions figure out that these Hispanics would vote strongly Democrat if legalized, and so they flip on the issue and now demand a SWEEPING AMNESTY. The Dems, of course, have no choice but to comply (not that they had anything against this strategy), and hence their flip (as evidenced by contrasting Obama against Bill Clinton’s clip above), and the huge push for Amnesty begins. The Dems, since they have Republicans needing the workforce, make a gambit, they will not compromise for anything short of a full, general, amnesty. If the Republicans wanted the millions of workers, they would have to let those workers ultimately vote. This was then coupled with the propaganda campaign which convinced the idiot Republicans that the white vote was always going to be split down the middle (or maybe lean slightly Republican, at best), and so the idiot Republicans better get on board with Amnesty so they could fight for a few of those Hispanic votes...otherwise they were doomed forever.
Of course no one bothered explaining to fly-over country why Amnesty was a good idea for Americans, simply because it was not possible, but then who really cared about fly-over country when all the votes you needed were in DC and ready to go your way.
So the Republicans opened the floodgates out of economic self-interest, and the Democrats WEAPONIZED Immigration as a political tool (and for that, they committed treason), and you had everything going in one direction, right up until 2014 when, days before a final vote on the permanent transformation of the US (into a 3rd world country), when a relative handful of people in one Virginia Congressional District (with the help of God) threw Eric Cantor out of Congress. That stalled the issue long enough for Trump to figure out how to win on it.
That’s a great summary.
Great history lesson. Thank you!