Republicans have by far and it's not even close benefited by partisan gerrymandering over the last 10-12 years. Between 2012-2016, 59 seats in the US House of Reps were affected by partisan gerrymandering with Rs netting 39 seats. These were all done in mid west and southern states mainly.

The overarching point of my post is the cognitive dissonance in the behavior. You can't say allowing immigrants to skip the lines = more Dem votes (when it doesn't), while actively changing the rules to get more votes because your policies suck!