Southern Dems did a lot of stuff to restrict the vote, not just to Black voters. They opposed the 19th Amendment pretty universally, even though Dems in western states were some of its strongest supporters. They also had really restrictive voter laws. The Virginia constitution of 1902 probably restricted the vote to about 20% of Virginia's population.

B/c of the senate and house districting, sometimes it makes sense not to grow your voting base in the US, but to concentrate on restricting votes that you can't control. You can modern equivalents of it now in some states.