MARK HALPERIN: Why is the Trump campaign defiant about this, rather than just quickly explaining --

MIKA BRZEZINSKI (CO-HOST): And even apologizing. How easy.  

HALPERIN: Yeah. 

ROBERT COSTA: The first question many people had when this occurred is how did this happen? Most presidential campaigns have 15 to 20 people on the social media team reviewing Twitter messages, if not more people. But I think this is indicative of how the Trump campaign operates. They for a long time have retweeted messages from supporters without vetting those supporters. And Trump has had problems in the past with people who have associations with white supremacy or anti-Semitism giving him support on Twitter,and then Trump integrates them into his own Twitter feed. And there's another sphere of the web -- this is important to understand -- called the alternative right, quote, the alt-right. And this is a sphere of the web that's kind of the hard right. It includes some anti-Semites, it includes some white supremacists. And they operate kind of under the radar of the national conversation. And some elements of this alt-right, that has gotten an increasing presence in American politics, has migrated toward Trump. That doesn't mean Trump endorses them. But they have more and more appeared at his rallies and in his social media as supporters. And one of these images that is often appearing on those alternative right websites, that's the same image that was tweeted by Trump that included the six-sided star, the star of David. And so the Trump campaign doesn't have this vetting operation, and so it's not that surprising that it somehow appears on Trump's feed. 

BRZEZINSKI: Nicolle, I just -- I'll toss it to you and you can jump in. But the problem here is that it is part of a serious pattern that is on the record. And if by any chance this was some wild mistake, why not just apologize profusely, immediately?

Related:

CNN: Donald Trump's 'Star Of David' Tweet Controversy, Explained

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CNN Highlights How Anti-Semitic Trump Fans Attack Critical Reporters

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“Trump Is Right”: Trump’s White Nationalist Backers Applaud His Racist Attacks On Federal Judge