Endorsements don't influence opinion? Horseshit.
As I've stated repeatedly, I am indifferent as to which Democratic candidate ultimately becomes the nominee. Any of the choices would be fine, and whichever is the nominee will earn my unflinching support.
That does not mean, however, that my vote in the Primary will be a random selection. Having been mildly browbeaten for my declaration that I'll make that decision on the day I vote, I'll reiterate, again, that said decision will be based on contemporaneous observations - one of which is that which is informed by who, among those with a working relationship with the candidates, has recommended whom by way of an endorsement.
I do the same with many of the decisions in my life. I rely on the mechanic with whom I've established a trusting relationship to provide advice on the maintenance of my truck. I look to those I know in any given industry, if available, to assist me in making decisions about important purchases. And I consult with those who know me best to help guide me through my perilous existence.
Accordingly, I incorporate each candidate's contemporaries' recommendations - if said contemporaries are individuals whose opinions I generally trust - into my voting decision. Those individuals' perspectives are based upon factors beyond my purview. I don't know any of these candidates, and they do. To suggest that I should ignore their professional opinions is asinine.
On March 15, I'll cast a vote for a candidate based upon that candidate's platform, composure, electability and, of course, the advice of others.
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But I certainly don't disregard them, either. And not because they reinforce my opinions but, rather, that the individual(s) making the endorsement(s) most likely have an informed reason for doing so that's outside my purview. It may even clash with my opinion but it nonetheless is informative.
Celebrity endorsements can be useful too, as long as the celebrity is hawt. 
