If every state did it (which will never happen), then the electoral vote would essentially mirror the Congressional vote. The last time I looked, the Democrats lost a majority of the Congressional districts.
Careful gerrymandering could fix that, but it would require that Democrats first elect governors and state legislatures that would fix it for them. The last time I looked, the Democrats lost a majority of the gubernatorial and state legislative elections too.
The only thing that would fix the Democrats current problem would be a straight popular vote, so that the Democrat controlled urban areas could rule all of the stupid people in flyover country who don't know enough to vote for socialist candidates.
They want to award EVS based on popular vote of the country regardless who won their state. National Popular Vote Interstate Compact
But even in my state of Illinois which is already as heavily gerrymandered as you can possibly get, it would split the EVs in a much more favorable way. Just compare the map I posted with the IL CD map and you’ll instantly see that while the blue population centers (mostly Chicago) can win statewide majority they cannot do so in each CD. If the worst cases of gerrymandering were corrected (which may happen even thought the courts refused to allow the most recent referendum to appear on the ballot), a sane map would allow the red areas of the state to become a plurality.