"Demographics is destiny" seems to be a quote from a french philosopher from the 1800s, while "coalition of the ascendant" seems to be a description of the coalition Obama sought to build in his second term, an idea swiftly dismantled in 2016.
The articles I can find discussing these things don't contain any democrats scheming about using immigrants to overtake the republicans. The only people I find talking about how it will "estrange the republican party from these growing demographics" are republicans. I'm not going to claim that no democrat has ever considered that outcome, but I am going to propose that it seems more likely to me that if that were to happen it would be a result of politics they'd be in favor of anyway.
In general, it's pretty popular to help people. I don't think republicans would disagree that part of their coalition is built on higher income individuals, which they hope to grow by raising incomes. They're not doing that as a sort of underhanded tactic, they believe income is good. In the same way I think the Obama democrats do believe in helping immigrants, and obviously that makes them more popular amongst immigrants. That's not a scheme, that's just a policy.
I don't think this is nearly as clear cut as you believe it is.
But what was the nature of "the coalition Obama sought to build in his second term?" Normally, political coalitions are based on things like geography or economic classes. But Obama's coalition was based on ethnic groups. Specifically, it was based on winning supermajorities among demographic groups that were rapidly growing due to immigration. Indeed, the results of the 2016 election were portrayed in U.S. media as being the last gasp of the old America before it was washed away by demographic change.
Respectfully, maybe this would be clearer to you if you lived here, and spent the last 15 years reading countless headlines and articles about demographics, which were relatively rare before 2008. And those headlines and articles suddenly stopped last November, when Donald Trump won a narrow majority of naturalized citizens. None of that is a coincidence.
> The articles I can find discussing these things don't contain any democrats scheming about using immigrants to overtake the republicans... I don't think republicans would disagree that part of their coalition is built on higher income individuals, which they hope to grow by raising incomes.
That's a good comparison. But I think it's totally fair to say that Republicans have a policy of giving tax cuts to rich people because it inures to their political benefit. Republicans obviously never say that in those words, but Democrats certainly characterize Republicans that way. And I think it's a fair criticism.
I have heard commentators mention ideas along those lines (never the specific formulations you used as examples, but the general vibe) post 2016, and even a little before that. That is, to me, not the same as that being the policy. Post 2016 democrats needed a cope. They needed a hope to hold on to after they had lost, what to them seemed like a slam dunk. That's not a policy proposal, but rather a strategic observation. In general I think you're better served by listening to politicians when they are trying to build, than when they have failed in building.
I also think it's quite important to note that in that analysis, we presuppose that immigrants will like the democrats. That either requires that democrat policies are good for immigrants, and immigrants to recognize that, or a vast conspiracy to take America down. If demographic change would turn America into a third world country, as some commentators have argued, surely immigrants wouldn't be for that either.
> But I think it's totally fair to say that Republicans have a policy of giving tax cuts to rich people because it inures to their political benefit.
I surely don't hope it's that direct. I think it's fair to talk about the cause and effect, but it would be totally unfair to characterize it as naked corruption. I truly believe that the mainstream American republicans believe in tax cuts as a means to drive innovation. That they believe in slimming down the government from a place of ideology, and not simply a naked ploy to reduce the oversight of their sponsors' activities. That they believe their policies to increase the wealth of the regular American, which they then hope will make them vote Republican.
I worry that this is no longer true of the "far right"/"alt right"/"authoritarian right". That distinction, between doing something for a belief in a better world, and doing it purely for strategy to gain power, is where I place the line to "fascism". A definition I don't share with many scholars.