I've written about the attempts to gerrymander the electoral college here at bluestategeorgia.
But summarized, the net effect would be much like the county unit system was in Georgia before it was struck down, of making the white vote count more than the African-American or Latino vote.
I'm not sure how seriously the GOP is willing to push this one, but if it were successful it would render the idea of "free and fair" presidential elections farcical, and in all likeliehood destabilize the electoral system as the minority population increased. A system in which one candidate wins the popular vote with a enormous margin, yet the other candidate wins, isn't a stable system.
More to the point, these proposals are overtly racist, and given the GOP's problems with minority voters, it's amazing to me that they seem poised to do this.