Sen. Al Franken Alan (Al) Stuart FrankenGOP Senate candidate says Trump, Republicans will surprise in Minnesota Peterson faces fight of his career in deep-red Minnesota district Getting tight — the psychology of cancel culture MORE (D-Minn.) on Sunday called on supporters to reject one of President Obama's nominees to the Treasury Department.

Franken criticized nominee Antonio Weiss in no uncertain terms, arguing Obama had nominated the wrong person for the job of Treasury undersecretary for domestic finance.

He argued Weiss would not put the middle class first and that he was too close to Wall Street.

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"Join me in asking the President to withdraw Antonio Weiss’s nomination," Franken wrote in an email to supporters on Sunday, with a link to the petition. "We need a nominee who will put the middle class first."

Franken wrote that Weiss has worked on manuevers called "inversions," which are mergers that seek to lower a company's tax burden in the United States by moving its headquarters overseas.

"More than six years after the crash, the American economy is still recovering," Franken writes. "We got into that mess because we were willing to let Wall Street police itself. Foxes make poor guards of henhouses. We know that through bitter experience, and I’m not willing to let it happen again."

Franken is joining Sen. Elizabeth Warren Elizabeth WarrenGOP set to release controversial Biden report Biden's fiscal program: What is the likely market impact? Warren, Schumer introduce plan for next president to cancel ,000 in student debt MORE (D-Mass.) and other liberals in opposing Weiss, setting up an internal Democratic Party fight with Obama. Weiss is an executive at the investment banking firm Lazard.

The White House has defended Weiss — and his values.

"He is somebody who has spent some time thinking about some of the issues that the president believes are critically important," White House press secretary Josh Earnest said earlier this month. "For example, in 2012, Mr. Weiss co-authored a report called ['Reforming Our Tax System, Reducing Our Deficit']."

Earnest said Weiss's experience was an advantage.

"This is somebody who has a very good knowledge of the way that the financial markets work," he said. "And that is critically important when you're asking somebody to take on a position in the federal government that has such a significant bearing on those markets."