How will Donald Trump supporters react to a Hillary Clinton win in the fall

[Absentee Voting Ghost of Ruin]

Civil War.

It begins when Trump, being his usual blowhard idiot self, calls for armed revolution to oust Clinton and install him in the White House. When challenged by Wolf Blitzer asking him if he really just called for an armed revolution, he'll hem and haw but basically say "yes".

His supporters will take him at his word, and pro-Trump militas will riot, attacking minorities, burning "democratic" buildings, etc. It will be moderately bad (low-end riots, with more guns than normal) but be in the process of being brought under control. Donald, however, will continue to urge his supporters to "fight back". He'll continue to get media coverage, although the direct coverage will become increasingly fringe, with mainstream news (even FOX eventually) refusing to deal with him directly, and only reporting on his interviews with places like Newsmax.

Since it will never occur to his tiny little self-absorbed brain that he could be held  accountable for anything, it will come as a complete shock to Trump when his home is stormed by heavily armed federal officers with a warrant for his arrest on charges of treason. He'll open fire on the arresting officers, killing one and injuring several.

Trump's arrest, trial, and subsequent execution will only enrage his supporters still further,  and his cause will be taken up in the media by a range of right-wing and celebrity nutjobs and attention seekers who encourage Trump Terrorism. This sets the stage for decades of smouldering guerilla war, as Trump Terrorists attack government officials, minorities of every description, famous landmarks, public buildings and transit and other random targets.

The US descends into a police state in an effort to stop the random, at most semi-coordinated violence. Areas with large levels of Trump Terrorist support start to resemble the Middle East, where comparatively anti-Trump areas are no worse off than Great Britain during the Troubles.

Centuries from now, Americans celebrate Dump on Trump day every year, the day before election day, by ceremonial public defecation on orange mannequins across the nation.