Here is the thing, we don't need immigrants to vote. In the 2020 election which did he an increase of voting only around sixty six percent of legal voting age American citizens were registered and voted. There is no need to bring over millions of people from the South, and get them to vote. All we need to do is get that thirty three percent who don't vote, to want to. The numbers are already there.
Using Southern migrants as voters would be too easy to track, would leave a lot of evidence and democrats are way to incompetent to pull it off.