I’ve been looking for data to back up this assertion for nearly 20 years, and I haven’t seen it.
In 2020, by raw votes the Democrats should have gotten 224.0 house seats instead of the 222 seats they actually got. If voter suppression was really a big thing you’d expect to see lower percentage of black voters, in reality since 2008 black voters vote at an equal rate to whites and when you adjust for factors like education in some elections they vote at a higher level. Latinos do vote at a lower rate, but there is a pretty simple explanation, a large number of Latinos aren’t citizens.
I’m convinced that there are two lies each party tells their base to generate enthusiasm and for fundraising. For Republicans, it is there is widespread voter fraud, and illegal voting. When I was poll watcher in 2000-4, a couple of Republican lawyers flew all the way from Washington DC to Hawaii to train us. They used lawyerly language like “suspicious, reports” to suggest there was a lot of illegal activity by the Democrats at the polling places. It is easy to see how less scrupulous, knowledgeable folks doing the training would skip the qualifier and just say Democrats flat-out cheated, voted twice, filled out the union workers ballots etc… As we know this 20+ year lie eventually morphed into the great Donald Trump lie of the 2020 election.
For Democrats, the lie, is that things like voter id, suppress black votes. The SCOTUS case on voter ID. Crawford v. Marion County Election Board, the most interesting thing was the finding of fact by the lower court. Neither the Republican nor the Democrats were able to find a single example to back up their case. Republican couldn’t show any instance of voter fraud, and the Democrats couldn’t show any example of how getting an id would be a great burden to a voter.
Now that’s not to say that Republicans don’t try to suppress votes, they do it is just that aren’t successful in it making a difference. The George election law was a great example. If you listened to CNN and MSNBC crowd it was Jim Crow 2.0 But if you actually listen to somebody who knew what they were talking in this case Georgia’s Secretary of State Brad Raffensperger, and CNN host that actually gave him air time talk Anderson Cooper, but not Don Lemon, you found out the truth. The truly awful things, were proposed amendments that never made it into the bill. Ballot access for everyone in Georgia is a lot easier than in places like Delaware and many NE states.
But the ultimate proof is in the results. Georgia is still a red state, but if the Republican-run an awful candidate like Trump, or Walker, and the Democrats run a moderate candidate like Biden, or Walker they can win and blacks will turn out in large numbers to vote for them or against the other guy.