They're not going to affect the 2020 elections, nor elections for a few cycles after that.
But... it's the illegals -today- the are the problem.
The problem is they are having anchor babies who are brand-new citizens and who -- in 18 years' time -- will become voters.
And... most of them will "vote left".
And then... these [formerly] "red" states ain't gonna be red no more...
If you get the color of my argument...
Actually the problem IS right NOW at the border. Those granted asylum are eligible to apply for citizenship within a 5 year period. That means quite a few of them will more than likely be eligible to vote in 2024.
Consider also that there is a migration of people from less than affordable states like CA into more affordable states that are currently red, possibly flipping a state from red to blue.
All things considering what is currently happening either intentionally or unintentionally is favoring the DEMS. Perhaps not in 2020, but most definitely in 2024.