By Richard Cowan
WASHINGTON (Reuters) - The U.S. Senate was poised to vote on Tuesday on President Donald Trump's choice of billionaire Betsy DeVos to be education secretary, amid a deadlock over the controversial nominee that is expected to be broken by Vice President Mike Pence.
According to Senate officials, there are no records of a vice president ever before being called on to break a tie vote on a president's Cabinet pick.
Following a rocky Senate confirmation hearing, Democrats have attacked DeVos as being unprepared to lead the Department of Education.
Historically, Cabinet nominees with weak support in the Senate ask the president to withdraw their nomination. But DeVos has shown no sign of backing down.
With 46 Democrats, two independents, and two Republicans expected to vote against DeVos, that leaves only 50 Republicans thought to be supporting her in the 100-member Senate.
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 Corporation, a Michigan car parts supplier and sister of Erik Prince, the founder of the security company formerly known as Blackwater USA, now called Academi.
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.
So far, no Republican senator other than Susan Collins of Maine and Lisa Murkowski of Alaska have come forth in opposition to DeVos.
As the debate wound down, Senate Democratic leader Charles 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 would promote charter schools in a way that would undercut public schools, which have long been the anchor of the U.S. education system.
Once the Senate votes to confirm or reject the DeVos nomination, it is 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 Pudzer to be secretary of labor. Pudzer, the chief executive of CKE Restaurants Inc [APOLOT.UL], has admitted to employing an undocumented immigrant as a house cleaner.
Under the U.S. Constitution, the vice president also serves as president of the Senate. As Senate president, he has the power to cast votes only when there are ties on nominations or legislation.
(Additional reporting by Lisa Lambert and Sarah Lynch; Editing by Frances Kerry)