Given that republicans have lost the popular vote in every election since 2000 I don't see them getting on board with going to a straight popular vote anytime in the near future to determine the Presidential election.
> Given that republicans have lost the popular vote in every election since 2000
They also just don't devote resources in heavily blue states for the Presidential race.
Why work to gain votes in a race you will lose anyway? Particularly given that you can win without putting in that effort.
Campaigns are optimized for the rules as they exist. Changing the rules changes the game. Just because the proposed rules look favorable to one side doesn't mean that they would remain that way if the changes took place.