He got his state on the national popular vote interstate compact as govenor. He's talked about it before and done more than most to make the popular vote a reality
The popular vote compact is a work around that doesn't require constitutional ammendment. It's an agreement to put their states delegates vote toward the winner of the national popular vote. (And only goes into effect once a majority of the electoral votes have signed on to it)
So far 209 of the needed 270 electoral votes have already signed on
There's still the electoral college which needs to go, creating a half-assed workaround which could easily be dissolved is not a fix. It's nothing other than a spit and a handshake