Is there any polling on this?
I know Colo has gone from solid red (2004 +5 Bush to solid blue (2012 +5 Baraq) in a very short time.
My idiot niece got priced out of NorCal and moved to Colo, apparently representative of many similar plus a swarm of illegals.
The Colorado Republican party was severely damaged by Governor Owens and Dick Whadams. They are still in disarray. The Dan Mays nomination caused a meltdown handing the Governorship to Hickenlooper.
It is hard to believe a sudden influx Californians made the difference. We were aware of the influx and gradual change.
A better explanation might be that the change has been gradual and that Dems only have a very slim margin right now. And they exploited that margin to pass gun control and other issues. Pretty much the story of the rest of the nation.