Obama's accomplishments will be destroyed. Obamacare will be repealed and the millions of newly-insured people will be thrown out in the cold again (it hardly matters whether the Republicans bother to "replace" it with some half-assed scheme of their own). The nuclear agreement with Iran will be abrogated and our government will likely make that country a primary foreign scapegoat, returning relations to pre-Rouhani enmity if not worse. The US will abandon the Paris climate agreement and return to reckless exploitation of fossil fuels and official denial about global warming.
It will go further than that. The Supreme Court will be packed with activist ideological wingnuts who will remain long after Trump is gone. Gay marriage, abortion rights, minority voting rights, separation of church and state, and what few institutional protections workers still have are all in serious danger. Even Social Security and Medicare could eventually be destroyed ("privatized"). Ethnic and religious minorities will come under attack, not only from hostile government policy but also from a racist subculture massively emboldened by Trump's victory. If those minorities react violently, that will be used to justify all kinds of "security" measures which will accelerate the slide toward fascism.
Very likely the economy will collapse as Obama's policies are replaced by a combination of Trump's random blundering and the standard Republican tax-and-spending cuts which have created such a mess in, for example, Kansas. The resulting unemployment and shortages will intensify racial and class polarization and bring a government witch-hunt for scapegoats, domestic or foreign, on whom to place the blame for "sabotaging" the economy.
Given the importance of the US to the global economy and the tremendous uncertainties that the mere prospect of a Trump Presidency have already produced, the economic disaster will likely be world-wide, leading to similar upheavals and threats to democracy in other countries. Worse, given Trump's ignorance and belligerence, the US is likely to become a rogue nation, using its vast military power to bully and threaten and worse. Even if there is no actual act of genocide, the world order as we've known it since 1945 has depended on the US as a guarantor of security and stability. It's unclear whether that role will continue; certainly the world-wide assumption that it will has been badly undermined. If Trump replaces Obama's nuanced Middle East policy with the kind of general anti-Muslim belligerence he has expressed during the campaign, millions will become radicalized against the US, and groups like Dâ'ish and al-Qâ'idah and their likely successors will gain new strength. There's also the matter of Putin's influence over Trump, whose extent and nature are still unknown. Europe could be in more danger than the Middle East.
I expect the US left to now dissipate a great deal of energy debating the exact nuances of how this disaster came about and how things could have been done differently. Would a more aggressive or more conciliatory campaign have produced a better result? Would Bernie Sanders have done better against Trump? Did third-party votes rob Hillary of victory in a few critical states? Did Republican efforts at vote suppression make the difference? Would Trump have lost if the media had been more forthright about him and less fixated on even-handedness? All of this will be as useless as the political-analysis sites' descent into navel-gazing about how the polls could have been so wrong. What happened is what happened.
Worse, even more energy is likely to go into throwing blame around. The Sanders/Warren wing of the Democrats will blame the Clinton/Obama wing and vice versa. Minorities will blame white liberals who didn't feel quite as threatened by Trump and didn't focus enough on stopping him. Moderates will blame radicals for overreaching and provoking the troglodytes who made up Trump's base, and radicals will blame moderates because, well, they always do. Everyone will blame the media. Much of this rancor will be expressed in faux-dramatic one-sentence paragraphs and in swear words typed entirely in capital letters. Some or even most of these accusations will have some merit, but the point remains that the only practical effect of such scapegoat-hunting and bridge-burning will be to profoundly weaken the left and sap its ability to take advantage of any opportunities which the new regime's incompetence offers us over the next few years. Our strength has always been in our ability to remain unified despite differences. Trumpism in practice is likely to provoke plenty of backlash and buyer's remorse, but a left divided into warring camps trying to blame and purge each other will not be able to exploit these. The best one can hope for is that our side gets those impulses out of its system by 2018.
There are a few glimmers of hope. Arpaio lost and Cortez-Masto won. Legal marijuana won. Growth of the non-religious and Hispanic populations will continue to work in our favor. Democratic governments in the blue states where many of us live will try to shield us from some of the worst effects of Trumpism. Popular culture will continue to be a subtle but powerful force changing social attitudes for the better. It's possible that Trump could resign in frustration if Constitutional constraints on his antics prove too strong, or that he could overreach so badly that even a Republican Congress would impeach and remove him. But that would leave us with Mike "God hates fags" Pence as President. Pence would be far less likely to incinerate millions of innocent foreigners in a fit of rage, and that's actually tremendously important. But domestically he would continue the massive reactionary shift of the government under more disciplined, more effective, and more explicitly theocratic leadership.
Moreover, the value of those "glimmers of hope" depends on the assumption that the institutions of the republic will continue to function normally. If they end up being subverted by the fascistic impulses and mob thuggery that Trumpism has already displayed, all bets are off. It's true that our institutions are much more deep-rooted and resilient than were those of, say, the Weimar republic. But the main institution one would expect to constrain Trump -- Congress -- is in the hands of that same Republican establishment which displayed such fecklessness and cowardice at every step of his rise from the beginning of the primaries. The courts may do a better job, but remember that the Supreme Court will soon have a wingnut majority including one and then more Trump appointees. It's seriously possible that within a few years everyone who has persistently spoken out against Trump -- not only MSM big fish but minor bloggers like me -- will be in physical danger from some sort of Internal Security whatever staffed by semi-literate goons with badges empowered to act out their resentment of pointy-headed intellectuals who can spell. Makes all that infighting with other factions of liberals seem a bit less worthy of your energy, doesn't it?
The best we can hope for is that democracy and its institutions do remain solid and that Trumpism provokes a huge backlash and that the Democratic party remains unified enough to take advantage of that backlash to regain Congress in 2018 and the Presidency in 2020. But even then, the new President will be starting from the same position as Obama did in 2008 -- cleaning up a gargantuan mess left by his predecessor (likely much worse than what Bush left), with little time or energy remaining to accomplish anything positive. What more he or she does accomplish will probably just repeat Obama's work that should have been built on by Hillary and will instead be wrecked by the Republicans.
And we'll have lost at least four years in the fight against global warming. This has direly increased the likelihood that humanity's very survival will depend, a few decades from now, on a desperate gamble on some giant planetary-engineering scheme to keep the Earth as habitable as possible for ourselves while most of the natural ecosystem is irrevocably lost.
Sorry, but I can't come up with any scenario more optimistic that this except by resorting to fantasies, such as Trump turns out to be the closet liberal that anti-Trump Republicans have accused him of being, or this election result gets exposed as a gigantic Russian hacking operation and Hillary actually won. That's Alex-Jones-level stuff.
I'm 56 and frankly I don't have a lot of fight left in me. The main thing that's keeping me going is the hope that I've overlooked some critical point and things won't really be as bad as now seems inevitable. Rational people in 1933 or 391 may well have clung to such hopes. It's far more likely that the situation is exactly as it seems to be, and that the future that should have existed has been wiped out by a maddeningly spurious and arbitrary, but now irrevocable, confluence of events. Perhaps I should simply focus on getting what I can out of whatever time I still have.