I do not believe he is a credible threat. He has already dug much of his own grave.
He has implemented campaigns that are obvious threats to perceived civil liberties:
The Democrats are short sighted, and each one for themselves. Among themselves, they will smear Bloomberg for his policies, and decry him for the hypocrite that he is.
- Limit Tobacco Use
approximately 14% of American adults smoke. Think they'll vote for someone who acts to restrict them?- He has made moves to ban plastic straws
- His ban on the amount of sugary soda that can be purchased in one drink
- The money he spends on gun control will make the NRA look paltry, and yet he has an armed entourage.
There is a "yuge" difference between Bloomberg and Trump. Aside from the similarity that both are billionaires, Trump clearly stated that he was going to step on people, drain the swamp, and make America greater. So far, he's delivered. Bloomberg will say he will make our lives safer and better and has demonstrated that he intends to do this by controlling us.
Americans are a fickle bunch. When given the choice of freedom vs. restrictions, despite their restrictive liberal leanings, when you give a person a choice between a demonstrable path (Trump) and someone who has demonstrated a propensity to implement controls on their freedom, they will always choose the former.
You're right in that his positions and history make him unpopular, even with Dems... but as the DNC proved in 2016, the nomination is for sale. Keep in mind all the opinion polls before the 2016 primaries also showed most Americans had a negative opinion of HRC, as well.