A day after President Barack Obama seemed to dismiss him as a “bright shiny object” challenging a better qualified candidate, Democratic presidential candidate Vermont Sen. Bernie Sanders announced he’s blocking the president’s nominee to run the Food and Drug Administration.

Obama nominated Dr. Robert Califf in September 2015 to be FDA commissioner. But Sanders, along with fellow Democratic Sen. Edward Markey (Mass.), said Tuesday that he has placed a hold on the nomination, citing Califf’s close ties to the pharmaceutical industry.

“At a time when millions of Americans cannot afford to purchase the prescription drugs they require, we need a leader at the FDA who is prepared to stand up to the drug companies,” Sanders said in a statement. “We need someone who will work to substantially lower drug prices, implement rules to safely import brand-name drugs from Canada and hold companies accountable who defraud our government.”

Democratic presidential candidate Senator Bernie Sanders (I-VT) participates in a town hall forum hosted by CNN at Drake University on January 25, 2016 in Des Moines, Iowa. Sanders is in Iowa trying to gain support in front of the states Feb. 1 caucuses. (Justin Sullivan/Getty Images)

Democratic presidential candidate Vermont Sen. Bernie Sanders participates in a town hall forum hosted by CNN at Drake University in Des Moines, Iowa, Jan. 25. (Justin Sullivan/Getty Images)

Sanders is running neck and neck with Hillary Clinton in Iowa, and well ahead of her in New Hampshire, while closing the gap in national polls.

“Dr. Califf’s extensive ties to the pharmaceutical industry give me no reason to believe that he would make the FDA work for ordinary Americans, rather than just the CEOs of pharmaceutical companies,” Sanders reiterated.

Though its rare for a Democratic presidential candidate to rebuke a Democratic president, the move could allow Sanders to rally the left flank of the Democratic Party at a time when Clinton is clinging to the legacy of Obama. It is also consistent with the Sanders campaign, which is railing against corporations and has continuously cited the cost of prescription drugs.

While not offering a formal endorsement during a recent interview with Politico, Obama referred to Sanders as a “bright, shiny object” compared to former Secretary of State Clinton, who he said “can start here, day one, more experienced than any non-vice president has ever been who aspires to this office.”

Califf’s ties come from running a multimillion-dollar clinical research center at Duke University that received more than 60 percent of its funding from the pharmaceutical and medical device industry, including Merck, Novartis and Eli Lilly — which Sanders pointed out supported his university salary.

Califf is the deputy commissioner for medical products and tobacco at the FDA, a position he has held since March. He worked at Duke University School of Medicine and the Duke University Medical Center between 1982 and 2015. He held several positions before he founded the Duke University Clinical Research Institute in 2006 and served as its director.