There are two vital issues that will lead me put aside my preference for others and vote for Hillary Clinton in less than two months. They are basic to who we are and who we want to be as a nation.
1. Selecting an acceptable Supreme Court justice immediately and as many as two others over the course of the next four years. Trump's appointment would be closer to Scalia and Thomas than Earl Warren, Oliver Wendell Holmes or Louis Brandeis.
These new justices will determine some divisive issues--guns, abortion, voting rights, money in politics, trade, workers' rights, and a plethora of others--and we would hope their determination would help heal the fractures in our society, not intensify them. They can help return our democracy (which is now an oligarchy) to the people.
2. Having an adult in the position of deciding when and if we go to war and making absolutely certain that the president has maturity, thick skin, cool head and a full understanding that we can't use a nuclear weapon on a country because its president has insulted our president's ego. George Bush once said he attacked Iraq after 9/11 (with which it had no involvement) because Iraqi officials threatened his dad. We don't need that mindset with a finger on the trigger. War is god-awful. Nuclear war--which candidate Trump seems to believe is an option--should not even be a point of discussion.
There is a lot more to all this than these two huge issues, but everything else is secondary. I have no reason to believe that Hillary Clinton will be an exemplary president, but she has the potential to be quite good. The only potential Trump has is to wreck our country and quite possibly our world. That's pretty basic, I'd say.