Unfortunately, when you are the owner and president of your own company (even one as large as the Trump empire), you begin to think that you can do anything, surround yourself with yes-men, let your emotions rule your head, and gradually lose touch with reality. Trump is a poster child of this.
If Trump was someone who had to operate in a check and balance political or corporate system (say as a CEO of a public corporation), he would recognize that this was the time to cut his losses (irrespective of what really happen), have Lewandowski issue an apology and move on. But because in the past 20 years he made all key decisions himself, and has not had to apologize to anyone, he is just not getting it. And while his (ever shrinking) base is eating it up, he is probably ensuring that he couldn't beat anyone in the General Election.
Is there actually any evidence of this?
And btw, compared to all the borderline insane stuff Trump himself has said and done during the past year, I really do not think this is that big a deal (though the his campaign has handled it as hilariously as you'd expect). Certainly can't see many of his fans rethinking their support over it.
What the Trump "phenomenon" has unfortunately done is that it is causing everyone to question their own judgement, because Trump has so far "defied expectations". I don't have that problem - I never underestimated Trump in the primaries, but I will also not overestimate him in the General!
You ask for evidence - here are the latest polls and discussion thread titles, with dates (you can see all of them in the 2016 U.S. Presidential General Election Polls section -
https://uselectionatlas.org/FORUM/index.php?board=92.0):
03-24 Clinton crushes Trump in Michigan
03-23 Clinton ahead in California
03-22 Clinton leads Trump by 10 in Michigan
03-22 Clinton leads Trump by 9 in WI
03-20 Clinton leads Trump in PA
03-20 Clinton and Trump in a close race in NC
03-16 Clinton Leads Trump Significantly in New York
03-15 Clinton and Trump in a close race in UT
03-11 Clinton and Trump in a close race in AZ
As you can see, Trump is a dead man walking for the General Election (and the Democratic spin machine hasn't even begun its work on him yet)!
