At this point, if Trump remains as unpopular as he is now, VA/CO will stay in the D column in 2020, and AZ/GA/NC are in play. If there's an economic crisis, he'll (and tbh most Dems at this point to some extent fit this category now) sweep all states I mentioned, and put states like MT and IN in play. I suppose one could argue that in 2024-28, his programs will cause a backlash among suburban voters to break such coalition but I'm not sure how long that'd take to play out, especially if Bernie resolves the crisis. If I had to guess, we as a country would become a lot less polarized then and less divided into red and blue states, where a number of winning coalitions exist for both parties.
Just winning one or even 2 big win does not constitute a realignment. Even if Bernie say wins those Obama coalition states plus GA AZ NC they will still trend back to the GOP(trend not swing) meaning in future GOP wins they will be part of GOP coalition again ,meaning they don’t need to abandon Reaganomics to win. Only way they will be forced to abandon Reaganism is if they have to rely on the industrial midwest to win(and with a Bernie style dem Party their coalition still will be suburbs and sunbelt not the Midwest)
Reagan coalition in many ways was an extension of Nixon’s (the suburbs plus sunbelt coalition ) and by 1980 that coalition became the majority coalition in Presidential elections. This meant the GOP could afford to lose the North East , Industrial Midwest (with exception of Ohio) and still win elections so that meant the only way a democrat could win an election from 1980-2008 was if they were able to win those states and only way they could do that was by being neo liberal .
Similarly in the New Deal era only way gop could win was by winning the North East and much of the industrial Midwest And only way to do that is by nominating Liberal Republicans .
Realignments are geographical IMO not ideological
1932-1980: Politics were dominated by large urban areas, and blue collar areas which meant both parties had to be more economically liberal to win
1980-Present: Politics were dominated by The Sunbelt and Suburbs which meant both parties had to be more neo liberal to win .
If the GOP gets blown out during an election or two, it's bench would be decimated due to the fact in the short term ticket splitting is still high, and the party would be force to adopt, as its brand would be toxic for starting the crisis, similar to how toxic the Dem brand was post-Reagan (although the Dems had a large enough Blue Dog wing that feared losing their seats that they were able to adjust quickly and cooperate with Reagan). They'd most likely adopt by appealing to the suburbs but with a more socially moderate message, and one that doesn't seek to repeal reforms made by Bernie Sanders (or similar) since it would be toxic to the electorate. Would they still be economically right leaning? To some extent yes but at least be fairly pragmatic and probably govern in a manner similar to how blue state GOP governors do today.
If the Democrats go the Sun Belt strategy, it kills them in the Senate since that focuses basically on winning large states, unless they can appeal to the working class Midwest. Sure, that'd keep them out of the White House, but then the GOP can block everything in the senate and we're stuck with well more gridlock. You're stuck with a geographic re-alingment of sorts but fundamentally the government isn't working for anyone with that level of gridlock, unless there's a de-polarization that occurs with this sort of realignment, but without resolving the fundamental crisis, I don't see a reason for the electorate to de-polarize.
