A new study by Princeton molecular biologist and neuroscientist Sam Wang digs deeper into the effect of the Republican gerrymander, and finds that the gerrymanders in seven states were so powerful that they are the equivalent of 1.7 million Democrats simply deciding not to show up at the polls:
[G]errymandering is a major form of disenfranchisement. In the seven states where Republicans redrew the districts, 16.7 million votes were cast for Republicans and 16.4 million votes were cast for Democrats. This elected 73 Republicans and 34 Democrats. Given the average percentage of the vote it takes to elect representatives elsewhere in the country, that combination would normally require only 14.7 million Democratic votes. Or put another way, 1.7 million votes (16.4 minus 14.7) were effectively packed into Democratic districts and wasted.
Such gerrymanders can exist because five conservative justices refused to block partisan redistricting in a case called Vieth v. Jubelirer.
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