For over 100 years the key to the success of the Democrat party has been Democrats destroying the economic hopes of whole groups of people and then convincing the victims that the Republicans did it.
The current immigration extravaganza is a repeat of the only successful play in the Democrat party playbook; create an underclass of Americans who will vote Democrat -- or not vote at all -- while being blissfully unaware that the reason they are at the bottom of the ladder is Democrat policies.
After the Civil War, Democrats, and Democrat spinoffs like the KKK, stayed in power in the South, even though they were racists and there were lots of potential black voters, by using the strong arm of bigoted laws to keep Blacks where Democrats thought they should be. Democrats got the support of the non-racist whites by painting Blacks as dangerous and too stupid to be left to their own devices.
When the Great Depression started, Democrats feverishly leveraged what they'd learned and figured out an even better way to effectively exploit a whole class of Americans. By demonizing the people who'd brought about the U.S. post-WWI prosperity and by convincing enough Americans that FDR was all that kept them from starving, Democrats managed to get Roosevelt elected 3 times even though the economy didn't get any better -- we can write off his fourth election to the war.
The Democrats convinced Americans that without FDR the country would get even worse; and we all know it's always possible for things to get worse. They made a new underclass, something unheard of in America, who felt that they were entitled to being bailed out not by their fellow Americans but by the government.
It also taught them that a lot of Americans were just as willing to buy the big lie -- without FDR you'd be dead and Republicans only care about the rich -- as the relatives they'd left behind in Europe.