Story highlights Errol Louis: Bernie Sanders correctly pointed out Hillary Clinton's ties to Wall Street, with which she has a complicated romance

He says one author says banks, financial industry back her because they see her as one of their own who will protect their interests

Errol Louis is the host of "Inside City Hall," a nightly political show on NY1, a New York all-news channel. The opinions expressed in this commentary are solely those of the author.

(CNN) If Hillary Clinton wants to shut down the populist surge of Sen. Bernie Sanders once and for all, she'll need to do a better job of explaining, and perhaps untangling, her complicated romance with Wall Street.

Errol Louis

This includes not only the massive donations her campaign and the Clinton Foundation have received from gigantic financial firms, but the private speeches she has delivered to banking executives for eye-popping sums in excess of $250,000 per talk.

In a country where 42% of all employees are working for $15 an hour or less and a majority of voters want a higher minimum wage, Democrats seen as too close to Wall Street risk a backlash at the polls. The populist unease was on display during the most recent presidential debate, when Sanders, a socialist firebrand, accused Clinton of fostering, and benefiting from, a cozy relationship with big-money interests.

"Let's not be naive about it. Why, over her political career, has Wall Street been a major — the major — campaign contributor to Hillary Clinton?" Sanders asked rhetorically. "You know, maybe they're dumb and they don't know what they're going to get, but I don't think so."

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Irritated by the accusation, Clinton jumped in, complaining that Sanders "has basically used his answer to impugn my integrity," then pivoted to a novel defense of her actions -- namely, casting her catering to Wall Street interests as an act of patriotism in the wake of the destruction of the World Trade Center.

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