The 25-30% hard core right wing constituency is similar to the 20% hard left constituency, they have power only because "the center cannot hold."
Racism is too broad a brush, while there are racist elements (and always have been), cultural and social issues are more complex.
Abortion is a matter of belief, I don't believe in the existence of souls, so to me it's absurd, but if you do believe, it's logical.
LGBT is really about Democratic overreach, had they started with making all marriages "civil unions" as a legal matter, and left marriage out of the law and left it with religious institutions, you could have moved to full LGBT rights without demanding that a large part of the country accept that behavior as socially legitimate. There's is a difference between requiring legal tolerance and telling people you have to reject your religious beliefs because I find them reprehensible (and the same people defend Muslims who have beliefs that are just as retrograde).
The economic agenda really isn't about the Tea Party, it's about hijacking the populist right with an anti-government agenda (as if Jeffersonian small goverment rhetoric could apply in a modern industrialized society, but small town folk really don't understand how interconnected they really are until the grid goes down). But the hijackers then got wacked with an anti-globalization movement, which is not what the economic libertarians wanted. The populists are just angry, at government, at banks, at free trade, at corporations. Amd Trump reflects their intellectual confusion.
The working class have good reason to be anti-immigrant, in fact, there's a sizeable proporiton of Hispanic voters who want stronger immigration controls (because their wages are threatened the most). However, this is as much about call centers as farmworkers. STudies show the places that are most anti-immigrant are those first experiencing an influx of immigrants, once immigrants hit a critical mass where there are social interactions on a regular basis (defusing fear of the "other") and they become an essential part of the economic fabric, anti-immigration feelings subside. Immigration has been used to suppress wages, the H1-B visas weren't used for scarce technical personnel but to bring in mid-level guys to pressure Americans into taking lower wages. The "criminal and rapist" rhetoric is just that.
The medical insurance issue is really "I have mine, fu" issue. The majority of Americans get their insurance from corporations and government through tax subsidized programs (it's income, but not taxable, if you'r self-employed, you're paying with after-tax income for your insurance). If a single payer system is implemented, and corporation payments for health insurance were treated like income, most of these programs would go away. The upper middle class and rich would buy supplemental insurance on top of the single payer system (like with Medicare) and get better health care. So the vast majority of workers are happy to stay with the status quo, at least until they get laid off.
I thin the backlash against Global Warming comes from the holier than though attitude of many on the left, as well as smart propoganda by Koch brothers' financed groups. It's a difficult problem, whose impact won't be felt for decades, hard to explain because the "evidence" is primarily embedded in complex models that are innately untrustworthy (having worked on some complex energy/economic models in my time, I know first hand their limitations). So it's an easy issue to manipulate, especially when those who push climate change policies insulate themselves from the impacts (subsidies for solar panels and electric cars, and government full employment for environmentalists). Trust me, the majority of green entrepreneurs only care about one kind of green, and they're happy to let the taxpayers foot the bill and don't care about cost effective measures (or why we pour more money into solar panels than energy efficiency, and more money subsidizing development than supporting R&D).
The irony is that the Obama Administration was probably the most dedicated to "good Government," Cass Sunstein at OMB was a strong proponent of cost-benefit analysis, which is opposed by many on the Left who think moral imperatives should triumph at any cost, and we'll just finance our wish list by taxing the rich (but not the upper middle class). The Democrats have traditionally supported government unions who are the biggest obstacle to government reform - if you want to ask people for more taxes for more spending, you should be ensuring that you're spending govenrment money as efficiently as possible, and that government regulation is limited to those measures that clearly provide a net benefit. Unfortunately, this country has lost that middle group of politicians who believe in government but also are wary of rent seeking and featherbedding.
Trump is a gift to the Left, because as long as he's around, they can avoid the tough questions about how to govern, anyone can put together a wish list of programs and principles, but implementing them without bankrupting the country or enriching connected interests, and avoiding excessive intrusions into people's lives - thats the true art of politics and governing.