U.S. Sen. Susan Collins said Monday she will not support President Biden’s nomination to lead the Office of Management and Budget.

Without any Republican support, and with Democratic Sen. Joe Manchin of West Virginia opposing as well, Neera Tanden’s path to confirmation appears unlikely in a Senate that is evenly split. Another top Republican, Utah’s Mitt Romney, also said Monday he would not support Tanden. Alaska’s Lisa Murkowski, often a potential swing vote, has not indicated how she plans to vote.

“The director of OMB is responsible for overseeing the development and implementation of the federal budget and plays a significant role in any administration’s fiscal and regulatory agenda,” Collins said in a statement. “Congress has to be able to trust the OMB director to make countless decisions in an impartial manner, carrying out the letter of the law and congressional intent.

“Neera Tanden has neither the experience nor the temperament to lead this critical agency. Her past actions have demonstrated exactly the kind of animosity that President Biden has pledged to transcend.”

Collins also criticized Tanden – who previously led the liberal policy and advocacy group Center for American Progress – for deleting several hundred tweets in the days before her nomination was announced. One of those was a post that referred to Collins as “the worst.”

“Should Congress need to review documents or actions taken by OMB, we must have confidence that the Director will be forthcoming,” said Collins, who to this point had backed all of Biden’s Cabinet nominations.

Tanden has been relentlessly targeted by conservatives for her combative nature, which has included jabs at many sitting members of Congress. Progressives have countered that the outrage is hypocritical given Republicans continued support of former President Trump, who often wielded his Twitter account like a cudgel against opponents.

Tanden apologized broadly for her social media posts during her confirmation hearing.

“I deeply regret and apologize for my language – some of my past language,” she said. “I recognize that this role is a bipartisan role, and I know I have to earn the trust of senators across the board.”

With Tanden’s confirmation in jeopardy, it’s still unclear if Biden will pull her nomination and put forward another name instead.

“Neera Tanden is an accomplished policy expert who would be an excellent budget director and we look forward to the committee votes this week and to continuing to work toward her confirmation through engagement with both parties,” White House Press Secretary Jen Psaki said in a statement Monday.