Story highlights Democratic presidential candidate debate is October 13

Hilary Rosen: Clinton is going to have to call out Bernie Sanders at debate

Hilary Rosen, a CNN contributor, is a Democratic political strategist and managing director of SKDKnickerbocker and an adviser to the Democratic National Committee. The opinions in this commentary are solely those of the author.

(CNN) Hillary Clinton has one job in the upcoming CNN Democratic debate: She needs to convince Democrats that we don't need Joe Biden to enter the race to keep the White House. So, whether or not he shows up in Las Vegas on October 13, (CNN rules allow him to enter as late as the day of the debate), his presence will loom large.

Will Clinton be able to get the job done? It's a tall and complicated order for just two hours.

Hilary Rosen

For a start, Clinton will have to create enthusiasm for her pragmatic and deeply thoughtful policy-centered candidacy versus the leftist, pugilistic, feel-good rhetoric of Bernie Sanders. And she will need to do this even while fending off attacks from three candidates who have gotten zero attention, but who will still be participating in the debate: Lincoln Chafee, Martin O'Malley and Jim Webb.

This won't be easy, because even though Clinton's policies are no less sincere and authentic than those of other candidates, she has the "smart girl in class" problem. She speaks carefully -- you can see her thinking through what she is saying as the words come out of her mouth. That's because she is being thoughtful, yet instead of that being celebrated, people mistake it for being calculated.

Joe Biden, in contrast, has a natural laugh and a ready slap on the back. It's a guy thing, and it is appealing to many. It makes his policy pronouncements more heartfelt and genuine. Of course, as millions of women know, speaking carefully and choosing your words in the knowledge that they are going to be dissected is no more manipulative than the old slap em' on the back style. But for some reason the latter way is just more widely accepted.

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