Democrats want the ability to be able to change the rules of the Presidential race at the last minute if they think they may lose. That is, the Dem States want to be able to assign their electoral votes in whichever way will make their guy win.
This confuses the campaign, because the candidates would not know how to run. Do I go for the popular vote, or for the electoral vote? This would require two wholly and completely different campaign strategies. For example, Trump did not campaign in California at all because there was no point to it, with the electoral system. Most Republicans in California did not vote for the same reason, there just isn't any point to it. However, if they are campaigning for the popular vote, everything would be different. And Republicans all over the country, including those in deep blue States, would have a reason to vote.
Whatever the Leftist wackos want to do, the rules would have to fixed at least two years ahead of the election. Otherwise, the election would be chaos and no one would know what is going on.
As has been said, most of the time when the Democrats think they are changing the rules to their advantage, it winds up helping Republicans more than them. This may be the same case. If the Dems want the popular vote, Republicans could wind up burying them, as long as we all know the rules of the game ahead of time, and not after the fact as happened this last time.
In a one hundred yard dash race, it does not matter if Hillary ran two hundred yards. That does not make her the 'winner'. You cannot change the rules of a race, after the race has been run. And yet, that is just the Liberals are doing.