WASHINGTON (Reuters) – President Donald Trump’s choice of billionaire Betsy DeVos to be education secretary was confirmed by the U.S. Senate on Tuesday, but only after Vice President Mike Pence was called in to break a tie that threatened to defeat her.

The tie-breaking vote, which Senate officials said was unprecedented to confirm a president’s Cabinet nominee, came after two Republicans joined with 46 Democrats and two independents in opposition to DeVos. Critics have called her unprepared to lead the Department of Education.

Following a rocky Senate confirmation hearing, Democrats have attacked DeVos as being unprepared to lead the Department of Education.

Senate Democratic leader Chuck Schumer immediately derided the proceeding.

“This cabinet nom is so unqualified, so divisive, that @MikePenceVP had to drive down Pennsylvania Ave to cast the deciding vote,” he wrote in a Twitter post after the vote.

Under the U.S. Constitution, the vice president also serves as president of the Senate, with the power to cast votes only when there are ties on nominations or legislation.

Democrats kept the Senate in session throughout Monday night debating on DeVos and in an attempt to pressure one more Republican to join in opposition to DeVos and thus defeat her.

Ultimately, only Republican senators Susan Collins of Maine and Lisa Murkowski of Alaska joined the Democrats and two independents in opposition to DeVos. That left 50 Republicans supporting her in the 100-member chamber.

Historically, Cabinet nominees with weak support in the Senate ask the president to withdraw their nomination, which DeVos did not do.

DeVos is married to the heir and former CEO of Amway, which sells household and personal care items. She is also the daughter of the founders of Prince Corp, a Michigan car parts supplier and sister of Erik Prince, the founder of the security company formerly known as Blackwater USA, now called Academi.

As Monday night’s debate wound down, Schumer said of DeVos: “She disdains public education where 90 percent of our students are.”

Senate Majority Leader Mitch McConnell, urging her confirmation, said it was time to “end the unprecedented delay by Democrats” on the Cabinet nominations by Trump, a Republican who took office on Jan. 20.

DeVos has been an advocate of charter schools, which operate independently of school districts and frequently are run by corporations. Democrats are concerned she will promote charter schools in a way that would undercut public schools, which have long been the anchor of the U.S. education system.

The Senate is now expected to move on to debating Trump’s choices of Senator Jeff Sessions to be attorney general, Representative Tom Price to be secretary of Health and Human Services and ex-banker Steve Mnuchin to be Treasury secretary.

All three face opposition from Senate Democrats.

Also facing a rough ride is Trump’s choice of Andrew Puzder to be secretary of labor. Puzder, the chief executive of CKE Restaurants Inc, has admitted to employing an undocumented immigrant as a house cleaner.

(Additional reporting by Lisa Lambert, Sarah Lynch and Doina Chiacu; Editing by Frances Kerry)

IMAGE: Betsy DeVos testifies before the Senate Health, Education and Labor Committee confirmation hearing to be next Secretary of Education on Capitol Hill in Washington, U.S., January 17, 2017. REUTERS/Yuri Gripas