Plausible. Romney is getting demolished in the minority vote. Thankfully that won't affect the House too much because the minority vote is quarantined.
That means that the minority vote is gerrymandered so that it is concentrated in a few sure=thing districts (that will go 75% or so for the Democrat) so that far more districts can go 57-43 for the Republican.
Yes, it does. See North Carolina, South Carolina, to name 2, which are drawn to enact 4 Democratic districts, and 16 Republican ones at 57-43 or so.