I think Reagan Democrats are a dying breed and only exist in the fond memories of conservative websites like these. In reality, their numbers are probably insignificant.
They are indeed a dying breed, but some are still around. I talked to one at a wedding last weekend, he was a retired GM worker, union man all the way. Someone teased him about voting for H. Clinton and he laughed and said he may have to vote Republican for the first time since he voted for Reagan. He did not say who he might vote for, but yes the Reagan Democrats are still around for a few more years.
They existed pre-Internet.
From what I’ve observed among my acquaintances who may have been “Reagan democrats” at some point - is that liberal propaganda sites like Media Matters - Huffington... Etc.
This keeps them from wandering back over.
I think they are still out there, but mostly in retirement. Many of them were Hillary supporters back in the PUMA days. Where they stand now... who knows? I think there are enough of them they could tip a balance, and a lot of them are in blue areas too.