Sol's got me thinking about whether I"m an optimist as it comes to the future of US democracy. Perhaps I am. More specifically though, I'm pretty pessimistic about the near-term (say the next 1-4 years) but far more bullish a decade out. Similar to what tyort1 said, I think there's a 'tick-tock' that goes on; social issues get advanced, then there's a sharp reactionary pullback from those that are duped into thinking they somehow got 'left behind'. Generally these people aren't left behind at all, but succumb to the argument that things would be even better if not for all that leftest evil goin' on. Anyway, I digress...
Yes, I think its going to be a constant battle to keep health care and basic rights for large swaths of americans. Wacko idealogues like Moore will join other 'burn-it-down' extremests like Cruz and they might actually carry through on some of their promises. BUT - I don't think its sustainable. The GOP faced a choice after their 2012 defeat (the famous "autopsy") about whether to be a more inclusive, mainstream party (the committee's recommendation) or to continue down their plight-of-the-white-man rabbit hole. Obviously with Trump they chose the latter. But demographics is going to bite them in the ass in the long-term. Older white Americans are going to slowly die away, which overwhelmingly voted for Trupm and have supported this latest version of the GOP. Millennials are filling their ranks. While they still don't vote in the percentages that boomers do, by 2020 they will cast more total votes as the ranks of the boomers start to shrink (the oldest are already in their 70s). The Millennials are overwhelmingly in favor of gay marriage and by a strong majority support universal health care, but don't care as much about SS benefits. At the same time the country is becoming more diverse overall, with white voters making up a smaller and smaller portion.
Now I'm watching the GOP as it has doubled-down on its rich white base. Every time they've supported (or failed to condemn) racists tweets will make it that much harder to woo those voters in the future. It's simply demographics - over the next few election cycles their base is going to shrink relative to the broader population. By NOT being more inclusive and by directly attacking and scapegoating minorities they're going to make it much harder to flip these voters in the future. There's a lot of work that demonstrates that we develop our political ideologies in our 20s and once established they are very hard to shift. Right now we've got an historically unpopular president and congress among this vital future demographic. I doubt anything the GOP does after this president will make them look favorably on the GOP.
But what about gerrymandering? Right now we've got so many house seats that are so safe it supports tea-party candidates and other extremists. But gerrymandering works both ways. Its a wall to keep out the rising tide, but should the tide ever overtop the wall it becomes a bathtub where the water can't drain away, swamping those inside. The 2020 census should be eye-opening for the GOP (perhaps that's why they are currently underfunding it). As tyort1 mentioned, the biggest demographic shift has been from rural to urban areas. These wonky regions that are currently safe GOP moats are going to ahve to be re-drawn after the census in several states, and its going to take a lot more square miles of rural area for each district, diluting their power. The GOP lost the popular vote in hte last election, it could be much worse in the next.
Finally, should they ever get legislative momentum going they could be destroyed by their own actions. Right now they still blame all social ills on the last President ("thanks Obama!") but that goat can only be flogged so many times. Imagine they actually pass this tax reform are repeal the ACA. Even greater income disparity and millions of uninsured will almost certainly be the result, and they'll own that. Sooner or later a recession is going to hit and with each passing month its going to be harder to believably pin it on decisions by the previous administration.
in sum: the GOP has all the power right now and things will almost certainly get worse before they get better for progressively minded individuals. But the harder the GOP works to push their agenda the worse they'll do 7+ years from now. This could be a generational game-changer for republicans, but they are so focused on the 'now' they aren't (or won't) even consider the future.