WASHINGTON (AP) — The Senate was poised on Tuesday to confirm President Donald Trump’s nominee for education secretary by the narrowest possible margin, with Vice President Mike Pence expected to break a 50-50 tie, despite a last-ditch effort by Democrats to sink the nomination.

Betsy DeVos, a wealthy Republican donor and long-time school choice advocate, has emerged as one of Trump’s most controversial Cabinet picks. Labor unions have bitterly contested DeVos’ nomination, fearing that she will destroy public education by promoting charter schools and publicly funded voucher programs for private schools. Civil rights activists also fear she will do little to advocate for LGBT students and children with special needs.

Trump stood behind his nominee, accusing Democrats of fighting progress and change.

“Senate Dems protest to keep the failed status quo,” Trump tweeted Tuesday before the vote. “Betsy DeVos is a reformer, and she is going to be a great Education Sec. for our kids!”

Two GOP senators, Susan Collins of Maine and Lisa Murkowski of Alaska, have announced plans to oppose DeVos in a Senate split 52-48 between Republicans and Democrats. That will leave her with a tie vote if all other Republicans support her and all Democrats oppose her as expected, and will require Pence to put her over the top. A vice president breaking a tie on a Cabinet nomination would be a first in the history of the Senate, according to the Senate historian’s office.

After an all-night speaking marathon by Democrats, Sen. Patty Murray of Washington state, the top Democrat on the Health, Education, Labor and Pensions Committee urged her Republican colleagues to vote against DeVos, calling her unqualified and saying that she will be a poor advocate for low income families and students with disabilities.

“We are just within one vote of sending this nomination back and asking the president to send us a nominee that can be supported by members on both sides of the isle, that can set a vision that can fight for public schools, that can be that champion,” Murray said.

Her opponents also charge that DeVos has no experience to run public schools, having never attended one or sent her children to a public school.

“I am not just voting no, I am voting no way,” Democratic Senator Chris Coons Delaware said.