Republican Sen. Susan Collins will vote against the nomination of Neera Tanden to lead the Office of Management and Budget, dealing another blow to her chances of being confirmed after Democratic Sen. Joe Manchin of West Virginia announced his opposition last week.

Collins, a moderate from Maine, was seen as a potential Republican vote following Manchin's decision not to support Tanden. Democrats hold the Senate by a 50-50 margin, and Manchin's announcement was seen as devastating for her chances.

She cited Tanden's past criticisms of her Senate colleagues on social media for her decision and said the OMB nominee does not have the "experience nor the temperament" to lead the office.

"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," Collins said in a statement Monday. "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 continued that Tanden's deletion of tweets before her confirmation was announced "raises concerns about her commitment to transparency."

Manchin also said he would vote against Tanden because of her past criticisms on social media about Republicans, including Senate Minority Leader Mitch McConnell, as well as Vermont Sen. Bernie Sanders, an independent who caucuses with Democrats.

Senate Majority Leader Chuck Schumer said Sunday he is working with President Joe Biden to gather support to confirm Tandem. The President has said he does not intend to pull Tanden's nomination and that he believes they will find the votes to get her confirmed.

CNN's Lauren Fox contributed to this report.