I'm not sure what the big deal has been for the last two decades about "the middle class". Here is a short list of things the middle class already gets from the government as assistance:
Financial aid for college tuitions
Access to decent public schools for preparation for colleges
Mortgage interest deductions to subsidize home values (and make that inflated value available for loans)
Retirement accounts with favorable tax treatment (ROTHs, 401ks I'm less sure about).
Social Security and Medicare mostly flow to people with at least the modest means of the middle class, if not the rich or wealthy outright.
And this all results in:
Relative social mobility, both individuals and generationally, relatively steady incomes in stable jobs or easily transferable jobs skills, in all cases much more substantially so than that available to the poor.
What has changed, and what appears to be the reason it keeps coming up, is that there are now far fewer private unionized workers, particularly in manufacturing. But there are plenty of cops, teachers, nurses, skilled tradesmen, computer programmers, salespeople and so on who can fill in that void. Not to mention professional class incomes like lawyers or doctors or modestly successful salesmen/self-employed businessmen (who are not really "middle class" but all like to think of themselves as such). I personally don't see any particular reason why work in a factory should have been an automatic qualifier for middle class lifestyles and incomes in the first place (most of it is unskilled work requiring training, but not certification). But leaving that aside, the problem isn't really the "middle class" going away. The problem is access to middle class lifestyles is more difficult to acquire, particularly if one is poor.
We have as obstacles:
Poor public school systems with minimal to no training for college preparation. Few, if any, underserved neighbourhoods are putting kids in Harvard or Yale level institutions. Affirmative action seems more like a problem relating to poverty than race as a result (which sounds closer to the MLK ideal for it).
Licensing laws and certification for the most absurd protectionist justifications by existing players in a field or industry. Barbers and interior decorators should not need state sanction to operate. Doctors or teachers even have very tenuous arguments in favor of such sanctions (which I do not find persuasive, but many do).
Criminal penalties and enforcement strategies which lock up many poor people for trivial criminal behaviors (use or distribution of narcotics or other vice crimes like prostitution), further limiting access to development resources like education, damaging an existing family structures, and creating criminal records making it harder to acquire modest occupations.
Limited incomes and scarce resources that must be properly allocated according to a middle class set of values for advancement, without the knowledge of how that must be done, and in a situation of scarcity such that pooling and in-group loyalties must often take precedence over prudent sets of values concerning narrow self-advancement.
All of which creates a cycle of poverty that is difficult to escape.
In other words. I won't vote for politicians who drone on about the "middle class" or even "middle-income Americans", the bizarre Republican circumlocution version of the same thing. Perhaps there are real and tangible threats existing to the middle class' future as an institutional element of society. Most of those threats could be best alleviated however by properly dealing with the threats posed by poverty. The middle class, while not in possession of substantial resources, has enough available to deal with itself in more or less a sustainable way on its own. It is the poor who do not, and more importantly, do not have even enough to advance. Handing out more and more favors to special middle class interests is certainly a favored election tactic, for both parties, not just the expected Democrats.
But it is not a solution to the problems involved with the future of the middle class. So quit talking about it. Thanks.