Hillary Clinton viewed presidential rival Bernie Sanders' plans for breaking up banks and regulating finance as "naive and unworkable," according to a staffer whose account was disclosed in internal Clinton campaign emails obtained illegally and published by WikiLeaks Wednesday.

As the Vermont senator mounted a populist, anti-Wall Street challenge to Clinton during the Democratic primary, Clinton and some staffers thought she could blunt Sanders' advantage on financial issues by contrasting their plans, the email taken from campaign chairman John Podesta's account shows.

Clinton is "keen to find a way to keep going after [Sanders] on Wall Street (she's convinced his plan is naive and unworkable) as part of a broader indictment," wrote Clinton speechwriter Dan Schwerin.

Throughout the campaign, Sanders called for breaking up big banks and re-imposing Glass-Steagall, the Depression-Era separation of commercial and investment banks that had been officially repealed by Bill Clinton. That agenda drew praise from liberal activists.

Clinton, in contrast, favored tighter regulations and new rules on "shadow banks" — nonbank financial firms that are not subject to stringent regulations. The email shows campaign staffers and advisers developing a strategy for engaging Sanders on the issue of finance and discussing whether to present Clinton as tougher on banks, a tough sell to primary voters who viewed Clinton as more aligned with financial interests, or to try to avoid the subject because of the popularity of Sanders' stance.

"I liked messing with Bernie on Wall Street at a staff level for the purposes of muddying the waters and throwing them off their game a bit," wrote communicatons director Jennifer Palmieri. "But don't know that it is most effective contrast for her."

Mandy Grunwald, an adviser, cautioned against attacking Sanders on Wall Street issues, and counseled instead highlighting Clinton's experience to reassure voters that she wouldn't be bad in terms of regulating banks. Arguing that Sanders was weak on banks, she said, wouldn't be credible.

"Why is it not credible that he has really dumb plans for Wall Street?" staffer Jake Sullivan responded.

The winning strategy, as revealed in the primary debates, was for Clinton to highlight her plans for regulating shadow banks.

Ultimately, Sanders' run did influence the Democratic stance, with many of his positions, such as re-imposing Glass-Steagall, being written into the party platform.