Biden won 10 states on Tuesday:

1. Alabama  *
2. Arkansas  *
3. Maine
4. Massachussetts
5. Minnesota
6. North Carolina *
7. Oklahoma *
8. Tennesse *
9. Texas *
10. Virginia *

A simple google search for “voter suppression” in many of these states turns up a lot of results. Given that Biden attracts a more conservative voter base than Sanders and voter suppression is universally aimed at the left and disenfranchised, it’s not irrational to think that Biden received a bump in the primary from the results of GOP voter suppression efforts. Of the 10 states, 7 have experienced severe voter suppression issues in the recent past or present and of those 7, the only one where these seemingly have been fixed was North Carolina, where the racist ID requirement was struck down in court. I’ve marked these 7 with *.

Examples by state, link to source then relevant passages:

Block the Vote: How Politicians are Trying to Block Voters from the Ballot Box

“In 2016, Arkansas purged thousands of voters for so-called felony convictions, even though some of the voters had never been convicted of a felony at all. And in 2013, Virginia purged 39,000 voters based on data that was later found to have an error rate of up to 17 percent.”

Texas Closed Hundreds of Polling Sites in Black and Latino Communities

“The 50 (Texas) counties that saw the highest growth in black and Latino population had 542 polling sites close between 2012 and 2018, while the 50 counties with the lowest black and Latino population growth saw just 34 closures. The closures came despite the population in the top 50 counties rising by 2.5 million while the 50 counties that had just 34 closures saw their population fall by 13,000.”

https://www.splcenter.org/20200210/alive-and-well-voter-suppression-and-election-mismanagement-alabama

“There are numerous problems with Alabama’s voter roll maintenance protocols. Mailings, for example, are not the most effective way to communicate with a 21^st century citizenry. According to the U.S. Election Administration Commission, Alabama sent 416,632 confirmation notices to voters between 2016 and 2018. Fifty-five percent of those notices (229,407) were returned as undeliverable.¹⁰⁰ Another 138,830 notices were reported as “status unknown.”…Many of these confirmation cards were returned as undeliverable or were “status unknown” because a non-forwardable card is unlikely to reach voters who move often. Low-income people, apartment dwellers, renters and college students are less likely to have a current address on their voter registration record.”

https://www.theguardian.com/us-news/2019/jun/04/tennessee-law-aims-to-suppress-african-american-votes-lawsuit

“Last month Tennessee’s governor, Bill Lee, signed a law imposing restrictions on those groups holding voter registration drives, citing the high number of registrations collected by voting rights groups which are incorrect and become ineligible once filed to the state.

The law, once enforced, would fine those turning in incomplete or incorrect registration forms. In some cases, it could mean criminal charges. For example, a group that returns more than a hundred “deficient” forms could face a fine of up to $2,000 in each county “incorrect forms” were filled out. If more than 500 forms are found to be filled out incorrectly, that fine could be up to $10,000. It’s unclear what “deficient” and “incorrect” mean, both Johnson and Kristen Clarke, executive director of the Lawyers’ Committee for Civil Rights Under Law, the organization which filed a lawsuit on behalf of six organizations in Tennessee, told the Guardian.”

https://oklahomawatch.org/2019/03/30/502256/

“A review of Oklahoma’s purge of inactive voters in 2017 shows that Democrats were disproportionally affected.

Of the 167,011 who were deleted due to inactivity, about 46 percent were Democrats. Voter registration statistics before the purge, on Jan. 1, 2017, show that Democrats made up about 39 percent of all registered voters.

Republicans, meanwhile, made up about 33 percent of the purged inactive voters while making up nearly 46 percent of the pre-purge voter registration totals.”