There's already a thread a page back. Several good answers provided. These I found particulary good:
It didn't happen overnight. Back when Obama ran, he promised economic help toward many working-class people. Once in office, however, he didn't actually deliver as much economic help as he had promised (and he clearly could have done more than he actually did, even if he wasn't going to be able to do every single thing he promised), and when Trump came along, he also promised economic help toward working-class people, while Hillary largely campaigned on maintaining the status quo. Those things were the final things that flipped these voters.
I'd say it was around 2014/2015, when there was a huge inordinate amount of focus on police brutality, and when "wokeism" started to become the prevailing cultural ideology on the left, promoted by none other than Obama himself. He relentlessly promoted the idea that women were earning 70 cents on the dollar of every man (not true when controlled) and that black men are being discriminated against by police (true, but divisive). Remember that Obama also promoted the TPP that even most of his party was opposed to, and Hillary was waffly on. That probably had an effect on this demographic that was unfavorable toward international trade deals. People forget but Obama's approval throughout most of his 2nd term was pretty awful, only in 2016 did it imrpove, probably because most of the political discussion was off of him and on Trump and Hillary. A lot of working class areas were being won by Republicans in 2014, whether it was Elise Stefanik's northern NY district, ME's 2nd district with Poliqun, or Iowa's 1st district. That was a sign, even as Republicans still did way better in the college-educated suburban districts in 2014. But 2016 really was a dramatic shift in the political coalitions that not a lot of people could predict the extent of.
Related to this question is also this analysis by OSR, that I found convincing:
In many ways it is Barack Obama which is ironic given how different they are personality wise but actually thinks about it .
- Both rose out of seemingly nowhere to defeat major establishment candidates on both sides of the isle
- Both rose out of major dissatisfaction of the neoliberal consensus and on an sentiment that the US should be more non interventionist and focus on America first
- Both had strong cult of personalities that enabled them to have a very enthusiastic base of support .
- Both relied heavily on non propensity voters which led them to outperform polling expectations
- Both had extremely efficient electoral coalitions that had the tipping point states always far more favorable to them then the national popular vote
- Both of them resulted in a previously loyal voters of their party leaving while bringing in many loyal voters from the other party .
In fact I think without COVID 2020 would resemble 2012 and by 2024 Trump would have left the GOP decimated down ballot wise the same way Obama left the Democrats in 2016.
