Is today's Supreme Court 9-0 ruling, a state may require it's electoral college to vote along with the popular vote, a blow to Trump?

It would be the knock out blow. Trump would be down for the count.  Time to pack his bags.. but be sure to check them for White House silverware, especially the gold stuff. 

@anonymous who wrote "It is a blow to the constitution that allows electors to vote as THEY CHOSE" 

That is a statement by someone who does not know the Constitution. Plus it is the opposite of the electors voting as they choose, which is what they can and often do now.

They wouldn't be voting as they choose, they would be voting for what the majority of Americans chose. 

It is a blow to the constitution that allows electors to vote as THEY CHOSE

Actually no... it is a resounding defeat for the democrat radicals.

it might be a blow to him

It doesn't really change anything.  It certainly won't affect the outcome of the election.

It’s a blow to democrats. 

That's what it's always done. LOL