Democrats are speaking on the Senate floor for 24 hours in a last-ditch effort to derail the confirmation of Betsy DeVos, President Trump’s nominee for education secretary.

“Now is the time to put country before party,” said Minority Leader Charles E. Schumer (D-N.Y.), urging GOP senators to join Democrats in opposing DeVos, a Michigan billionaire and major Republican donor who has spent decades advocating the use of public funds to help parents pay tuition at private and religious schools.

“Her views are extreme,” Schumer said. “She seems to constantly demean the main purpose of her job, public education.”

DeVos’s confirmation vote is scheduled for noon Tuesday. All 48 members of the Senate Democratic caucus are expected to oppose her, along with two Republicans, Lisa Murkowski of Alaska and Susan Collins of Maine. Democrats need just one more Republican to flip to defeat the nomination, and they are hoping their 24-hour speech-a-thon will ratchet up the pressure.

Republican leaders have defended DeVos as a conservative who will scale back the federal role in public education, which expanded under the Obama administration. They have praised her as an outsider who will shake up the status quo to improve opportunities for disadvantaged children.

“This nomination is dead even right now — on the razor’s edge,” Sen. Patty Murray (D-Wash.), the ranking Democrat of the Senate Education Committee, said on the floor. Murray, who has a record of bipartisan compromise in the Senate, has been sharply critical of DeVos, arguing that she lacks the experience needed to lead the Education Department and promotes policies that threaten public schools.

“For the vast majority of people across the country, public education isn’t just another issue. It’s different,” Murray said. “We believe that a commitment to strong public schools is part of America’s core. The idea that every student, in every community, should have the opportunities that strong public schools offer. This is a notion that is embedded in our values. It’s who we are. It’s in our blood.”

Activists have targeted those Republicans who they believe have reservations about DeVos, particularly those from rural states, where alternatives to public schools — such as those promoted by DeVos — are few and far between. But other than Murkowski and Collins, no Republican has indicated that their support is shaky.

DeVos has come under fire for stumbling over basic education policy questions during her January confirmation hearing, at one point saying she was “confused” about a landmark 1975 law — the Individuals with Disabilities Education Act, or IDEA — that protects students with disabilities and their access to a free, appropriate public education.

Sen. John Cornyn (R-Tex.), the majority whip, praised Trump Monday for choosing a nominee who is not “another education bureaucrat that knows all the acronyms and knows the arcana known to people that have been brought up within that establishment.”

“Instead he chose an outsider, someone much like himself,” Cornyn said of Trump. “Someone more interested in results rather than paying homage to and feeding the education establishment here in Washington, D.C.”

If no other Republican defects, the Senate would likely deadlock at 50-50, requiring a tiebreaking vote by Vice President Pence. That would mark the first time a vice president’s tiebreaking vote would be needed to confirm a Cabinet nominee, according to the Senate Historical Office.

“We’re very confident that Betsy DeVos is going to be the next secretary of education, and it’ll be my high honor to cast the deciding vote on the floor of the Senate next week,” Pence said on Fox News Sunday.