Donald Trump's nomination of school choice activist Betsy DeVos as education secretary is on thin ice after two Republican senators vowed to vote against her.
Mrs DeVos, a billionaire Republican donor who spent more than two decades promoting charter schools, has emerged as one of Mr Trump's most controversial Cabinet picks facing fierce opposition from Democrats, teachers' unions and civil-rights activists.
With senators Susan Collins of Maine and Lisa Murkowski of Alaska in opposition, the nomination could die if Mrs DeVos loses the support of one more Republican and all Democrats vote against her.
Ms Murkowski said she believed Mrs DeVos has much to learn about public education.
"I have serious concerns about a nominee to be secretary of education who has been so involved on one side of the equation, so immersed in the push for vouchers that she may be unaware of what actually is successful within the public schools and also what is broken and how to fix them," Ms Murkowski said.
If all other GOP senators support Mrs DeVos, and all Democrats oppose her, she would end up with a 50-50 vote in the Senate and Vice President Mike Pence would have to break the tie to confirm her. A vote is expected in the coming days.
Senator Lamar Alexander of Tennessee, Republican chairman of the Health, Education, Labour and Pensions Committee, praised Mrs DeVos and expressed confidence she would be confirmed.
"Mrs DeVos believes in our children, their teachers and parents - she believes in the local school board instead of the national school board," Mr Alexander said in a statement.
"She's committed to public education and there's no better example of that than her work on the most important reform of public schools in the last 30 years - public charter schools."
White House press secretary Sean Spicer said he was not concerned about the defections by Ms Collins and Ms Murkowski.
"I have 100% confidence she will be the next secretary of education. She is an unbelievably qualified educator and advocate for students, teachers, parents," he said after the two senators announced their opposition.
In addition to the statements of opposition by the two Republican senators, a billionaire philanthropist and public education backer came out against her.
Eli Broad sent a letter to senators urging her defeat, saying Mrs DeVos is "unprepared and unqualified for the position".
He also said that if she were confirmed, "much of the good work that has been accomplished to improve public education for all of America's children could be undone".