this president is a clear and present danger to the long-term health of our entire system of government, yes, I will vote for whomever the Democrats nominate.
Can you even present any actual reason to believe this?
Sure, several. At a very base level, he has no problem debasing the legitimacy of our election process with wild and unverified claims of "millions of illegals voting" and claimed in 2016 that he'd keep America in suspense as to whether he'd accept the results of the election, if he lost. If he spoke in this way about an election that he won, imagine how he will respond if he loses in 2020. Given that the Senate is now basically a symbolic rubber stamp for the President and the judiciary can only pass legal judgments and not actually enforce their rulings, who's going to stop Trump from simply declaring the election null and void, essentially ending the American Republic, for the sake of his own ego? To top that off, he speaks of having the military, the cops, and the bikers - "the tough people" - on his side in case "things get bad". Do you really think that it's ok for a president to hint at who would take his side in the case of a civil war? That's extremely dangerous talk in such a polarized age. Whether he means it in jest or not, he has millions of people who would literally take up arms to keep him in the White House if he claimed that he was being forced out by some deep-state coup.
And of course, there's the fact that he openly invites foreign interference in our elections, blackmails allies into pulling up dirt on political opponents, and is able to commit crimes and violate the Constitution with impunity because of the aforementioned rubber-stamp Senate...so yes, Donald Trump is a threat to our system of government.
Good answer. You also forgot to mention that he has not just critiqued the media, but actually branded the free press - a necessary pillar of any functioning democratic system - the "enemy of the people." He routinely uses the term "fake news," an actual problem that should be appropriately addressed, to describe any news that is remotely negative for him politically. He's gaslit a huge portion of the population to the point where they will deny what is confirmed by many reliable media sources so long as Trump tweets out that it is a lie. The man being reported on has become his own reporter. The gutting of American media is an underrated threat to our system of government and while Trump is not the only cause, he is pushing the pedal to the floor.