From what I've read part of what the first two posters wrote is both true.
In regards to the second poster, he is correct that Bill Clinton won some of these former Reagan Democrats back in 1992 or 1996. However, many of the seemed to favor George W Bush over Al Gore in 2000, and contrary to what the second poster wrote, there is very little evidence that hardly any of these voters or, as the second poster wrote, these type of voters, voted for Barack Obama in 2008 or 2012.
Most of this 'working class' demographic had become fully Republican at the Presidential and Congressional level by 2000 over social issues.
The first poster is correct in that Politico recently took a look at these supposedly new voters that Trump brought into the primary process, and concluded that nearly all of them had regularly voted previously, just not in primaries. They also concluded that nearly all of them were long time Republican voters, though I'm not sure how they figured that out.
This. SOME of the "Reagan Democrats" came back for Bill in the 90s, though even then many supported Bush/Dole and Perot. It was in 2000 when Democrats lost this mythical demographic, and they haven't come back.
Anyway, it won't matter. The LBJ Republicans will come home to Hilldawg, deliver her Utah, and make this all a moot point.