Sen. Joe Manchin III (D-W.Va.) on Friday announced his opposition to President Biden’s choice to lead the White House budget office, imperiling her nomination in a narrowly divided U.S. Senate.

Neera Tanden, tapped to be director of the White House Office of Management and Budget, has emerged as a lightning rod for criticism over her prior attacks against Republican lawmakers and Sen. Bernie Sanders (I-Vt.).

If all Republicans vote against her nomination, Manchin’s opposition would prevent Tanden from being confirmed through the Senate, where each party only controls 50 votes. Biden has so far secured approval for seven of his cabinet nominees, and Tanden was widely expected to prove among his most controversial choices.

Asked while leaving Air Force One if he was going to pull Tanden’s nomination, Biden told reporters “no” and expressed confidence that “we are going to find the votes and get her confirmed,” according to a pool report. The White House also issued a statement defending Tanden.

“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,” Manchin said in a statement. “For this reason, I cannot support her nomination. As I have said before, we must take meaningful steps to end the political division and dysfunction that pervades our politics. At a time of grave crisis, it is more important than ever that we chart a new bipartisan course that helps address the many serious challenges facing our nation.”

With Manchin opposed, the path for Tanden to win the support of any Republican senator remains highly uncertain. At her contentious confirmation hearings this month, Senate Republicans repeatedly brought up Tanden’s prior attacks on GOP lawmakers, particularly on Twitter. Sen. Rob Portman (R-Ohio) cited tweets from Tanden calling Sen. Susan Collins (R-Maine) “the worst” and Sen. Tom Cotton (R-Ark.) a “fraud.” He also cited a Tanden tweet that said, “Vampires have more heart than Ted Cruz,” referring to the Republican senator from Texas.

Tanden has also compared Senate Minority Leader Mitch McConnell (R-Ky.) to “Voldemort,” the villain in the Harry Potter series, and called him “Moscow Mitch.” In August 2018, after Collins said she did not want to delay the hearings for Supreme Court nominee Brett M. Kavanaugh, Tanden wrote: “Pathetic.”

Sen. John Neely Kennedy (R-La.) on Feb. 10 scolded Neera Tanden, the nominee to lead the Office of Management and Budget, for her Twitter history. (C-SPAN)

Tanden has posted more than 80,000 tweets, and she repeatedly apologized for her prior comments in front of Senate committees. At one point in the hearing, Portman said approximately nine pages of tweets about Cruz remained live.

“I regret that language and take responsibility for it,” Tanden said at one of her hearings.

But those apologies seemed unlikely to mollify GOP opposition or save her nomination, particularly given some of her attacks have been against Collins — the moderate Republican typically considered among the most likely to break with party ranks. Republican support for Tanden’s nomination is “highly unlikely,” said one senior GOP Senate aide, who spoke on the condition of anonymity to candidly describe internal dynamics.

“I don’t see any Republican, at this point, bailing out her nomination. She seems to have burned too many bridges,” said Brian Riedl, a former Portman aide now at the Manhattan Institute, a right-leaning think tank. “Lawmakers are human, too, and do not like to confirm people who insult them.”

Even if Tanden can win the support of a Senate Republican, it is not clear Sanders would support her. Bitter fights emerged between Tanden and Sanders allies during the 2016 and 2020 presidential primaries. During her confirmation hearing at the Budget Committee, which he currently chairs, Sanders asked Tanden pointed questions about millions in corporate donations given to the Center for American Progress, the center-left think tank, under Tanden’s tenure. Tanden said those donations would have no impact on her decisions at the budget office.

Appearing on CNN, Sanders declined to comment on Friday when repeatedly pressed on how he would vote on Tanden’s nomination but did say he would be speaking with her next week.

A loyal Democrat and close ally of former secretary of state Hillary Clinton, Tanden was strongly supported by numerous Democratic lawmakers during her hearings. Several Democratic senators, including Sens. Cory Booker (D-N.J.) and Amy Klobuchar (D-Minn.), forcefully defended her tweets and past actions in committee hearings this month.

“A lot of people have said a lot of things on social media — probably people in this room — that they regret,” Klobuchar said.

White House spokeswoman Jen Psaki said in a statement Friday that the administration would continue working toward Tanden’s confirmation.

“Neera Tanden is an accomplished policy expert who would be an excellent Budget Director and we look forward to the committee votes next week and to continuing to work toward her confirmation through engagement with both parties,” Psaki said.

Manchin supported several of President Donald Trump’s divisive nominees over the previous four years. He was the only Democrat to vote for Kavanaugh.

Manchin was also among a handful of Senate Democrats to support Trump sending conservative firebrand Ric Grenell to Germany as U.S. ambassador. Grenell was previously forced to delete tweets, including ones mocking Newt Gingrich and the appearance of his wife, Callista.