It seems like many now-popular movements had deep-pocketed sponsors. Can a billion dollars always push an idea into the mainstream? Or are there counterexamples of groups who poured huge amounts of money into promoting something that never caught on?
Money does seem to be the only way to get even a hint of policy change from Washington, but the trend line of public opinion is opposite of what you suggest. Until around 1995, immigration restriction was overwhelmingly mainstream in the United States and still commands a strong plurality. https://news.gallup.com/poll/1660/immigration.aspx I'd further point out that the overwhelming majority of the moneyed interests…
George Soros does not, to my knowledge, employ a large number of low-wage workers- how would he personally benefit from a larger labor pool? The Koch brothers do have a very large workforce, but they're all industrial assets- hard to imagine farm laborer-types from Central America could be employed in huge numbers. The only people who could conceivably benefit from immigrant labor would be industries with huge huge numbers of minimum or close to minimum-wage employees- Home Depot, Chipotle, Subway etc. I guess Amazon.
Seeing as we have a federal minimum wage- how much money could an evil billionaire who employs thousands of unskilled workers possibly save with a larger labor pool? $1 per hour, per worker? $2 per hour? I find the amount of cost savings they'd get to be not that much- you'd think Evil Billionaire would put way more effort into healthcare reform, given that non-wage benefits are (much much much) more expensive than a few dollars per hour.
Saying 'the labor pool' is handwavey. Outside of a few industries, developed countries have mostly outsourced unskilled work to the 3rd world- so, if a bunch of farm laborer-types with a 6th grade education come here, they're not competing with the huge huge majority of skilled US workers. There is no affect on wages for most workers, and no motivation for really any white collar employer. I find your hypothesis unconvincing