Republicans have seen the writing on the wall. Decades of indicators have shown the majority of voters align with Democrats' policies. This is why Republicans have gerrymandered, suppressed votes, pushed voter identification, closed polls, and just generally tried to make it harder to vote or exclude people from voting. It's the only way Republicans have been able to win elections. The Republicans don't really have any ideas for public policy. And, they really don't care. Power is their ultimate goal. The power to control the purse strings of the government. Hence, they are continually trying to make it so that only those voting Republican can vote.
Republicans threaten a government shutdown unless Congress makes it harder to vote