Democratic Senator Joe Manchin announced Friday he will oppose the confirmation of Neera Tanden, Joe Biden's pick to lead the budget at the White House, potentially sinking her chances in a setback for the US president.
Tanden, the first woman of Indian descent to be appointed to head the Office of Management and Budget (OMB), has been the target of bipartisan criticism since Biden nominated her in November.
While she has earned the enmity of Republicans through her biting Twitter feed, Tanden has also come under fire from the progressive wing of the Democratic Party.
"I believe her overtly partisan statements will have a toxic and detrimental impact on the important working relationship between members of Congress and the next director of the Office of Management and Budget," wrote Manchin, a moderate Democrat.
"For this reason, I cannot support her nomination."
The OMB is a powerful department responsible for developing the president's budget and evaluating the projects and expenditures of his department secretaries.
The Democrats have a slim majority in the Senate, which has the power to confirm or reject presidential nominations: with 50 seats against 50 Republicans, they can count on the vote of Vice President Kamala Harris, who has the power to break the tie.
But with Joe Manchin's opposition, Tanden will most likely need at least one Republican for confirmation -- an unlikely prospect.
Biden showed himself determined on Friday to stay the course. "No," he replied to reporters who asked him if he was giving up his nomination.
"Neera Tanden is an accomplished policy expert who would be an excellent Budget Director," White House spokeswoman Jen Psaki said Friday, saying she continues to work for her confirmation with "both parties."
A first test will take place next week with a procedural vote scheduled for Wednesday in the Senate Budget Committee.
Tanden, 50, chief executive of the Center for American Progress, a liberal Washington think-tank, has been an outspoken critic of former president Donald Trump.
Some supporters of Bernie Sanders accuse Tanden of helping former first lady Hillary Clinton thwart the Vermont senator's 2016 bid for the Democratic presidential nomination.
During her career, she has focused on implementing policies designed to support working families, foster economic growth and reduce endemic inequalities, Biden's team said on announcing her appointment.