The fantastic amount of anti-Trump material pouring out across the media and throughout the whole of the left means they perfectly well understand the threat Trump poses to them. If they thought he was not a the most serious threat to the Democrats among the Republicans, they would stay silent and let nature take its course. They are not silent and are doing all they can to stop him. At the beginning they thought of him as the easiest one to beat and brought him forward out of the pack. Now they have seen the error of their ways and are pushing as hard as they can in the other direction.
I have just gone through Lucianne and the headlines there. It was near on a quarter of the stories were anti-Trump from every media source you could name. They mean it – the writerly class, they understand that he needs to be stopped, and of course this writerly class consist of almost as many Republicans as Democrats.