United States is a Constitutional Republic. Not a democracy according to the US constitution.
$ grep -i democra us_constitution.txt
$ grep -i republic us_constitution.txt
The United States shall guarantee to every State in this Union a Republican Form of Government, and shall protect each of them against Invasion; and on Application of the Legislature, or of the Executive (when the Legislature cannot be convened) against domestic Violence.
I understand you're offering this as a gotcha but I'm not sure what you're referring to and it's unclear from context.
In any event, both of those things are typically undemocratic which is why they are rare in functioning democracies and common in autocracies. No system is invulnerable to attack so in certain circumstances they aren't undemocratic. Excluding candidates for, say, a criminal record, mental incapacity, or foreign obligations is less democratic but no reasonable person would claim it voids the will of the people.
Not sure where you're getting the "overturned" part, but if you're trying to point out the the DNC runs roughshod over party members, then you're right only in the sense that they suck.
What sucks more is having a two-party system -- the game is pretty well rigged by that. Voters have the choice of the lesser of two evils. But at least there's a choice involved.
So, comrade, you have failed to sway me. I don't put party before country, even if I was a party member. I doubt you can say the same.
And the person they picked for this is a charismatic narcissist who clearly only cares about himself? The examples of previous "dictators" all clearly believed that what they were doing was for the benefit of the country as a whole.
Those opposed to Trump holding office don't do so because he's in the "wrong party", they oppose him because he is eminently unsuitable for the job. Note that even hard core conservative members of his party advocated for voting for his opponent. That's a first, and there's a reason why.
Note as well that he's making noise about ignoring a constitutional amendment that would prohibit him from the office after this term.