You can
take a look at a few states returns and notice something suspicious:
In IND, Dems won 2 of 9 House seats, both 65%/35%.
Missouri:
Dems won 2 of 8 seats, both landslides (81%/17% & 62%/36%)
No. Carolina:
Dems won 3 of 13 seats: all with 70% or more.
Ohio:
Dems won a mere 4 of 14 House races: with 82%, 73%, 68% & 61%
Tennessee: Dems won 2 of 9 districts: 80% & 68%
(not one competitive race -- the closest was a huge 29 point margin)
Texas:
36 seats. Dems won 13, a number with 70% or more. The GOP won 5 close contests, while the Dems only won one close race.
On the flipside, in Maryland, the GOP won 1 of 8 seats, 61%/38%.
Though none of the other 7 (Dem won) races were close at all, so even dispersing GOP voters from District 1 would not do enough to alter another race. I must say they have some bizarre-shaped districts in Maryland though.
Sure Dem voters tend to be compacted into urban areas, but it's often how you divvy up the suburbs that makes a big difference. And not hard to infer which states were gerrymandered.
Non-competitive races discourage participation, increase partisanship,
advantage incumbents, and otherwise hurt democracy and undermine faith in government.