The Senate is scheduled to vote Tuesday on confirmation of Betsy DeVos as education secretary, with the outcome expected to be the narrowest approval of a Cabinet nominee in the nation’s history.

The entire Democratic caucus of 48 senators is expected to vote against DeVos, as are two Republicans, Lisa Murkowski of Alaska and Susan Collins of Maine, who have said they do not think that DeVos is qualified for the job. The remaining 50 Republicans are expected to vote for DeVos, setting up a 50-50 tie that could only be broken with a vote from Vice President Pence.

“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.

It would mark the first time that a vice president’s tiebreaking vote would be needed to confirm a Cabinet secretary, according to Daniel Holt, an assistant historian in the Senate Historical Office.

And it would be the first time a vice president cast any tiebreaking vote in the Senate since Richard B. Cheney did so nine years ago.

[DeVos and her family are major donors to the senators who will vote on her confirmation]

DeVos has faced an unprecedented wave of popular backlash and partisan opposition: Since the Education Department was established in 1979, nominees to lead it have always been easily confirmed, often on voice votes or with unanimous support. The closest confirmation vote for an education secretary was 49 to 40 in 2016, in favor of John B. King Jr. Jr., who served during the last year of Barack Obama’s presidency.

But DeVos is unlike previous nominees in that she has no personal or professional experience in public education or elected office.

A Michigan billionaire and major Republican donor, she has spent three decades using her wealth and political clout to advocate for alternatives to public schools, particularly taxpayer-funded vouchers to help parents pay tuition for private and religious schools. She also has advocated for a loosely regulated variety of charter schools.

Republicans have defended her as an outsider who would challenge the status quo and as a conservative who would reduce the federal footprint in public schools. They are keen to change course after eight years in which the Obama Education Department exercised an unusually high level of influence.

But DeVos’s free-market approach triggered opposition not only from teachers unions, which mobilized considerable forces against her, but also from fellow education reformers who said they worried she was more committed to the ideology of “school choice” than to ensuring quality schools for vulnerable children.

DeVos was not widely known when Trump picked her in November. But that changed after her performance at a confirmation hearing in January, when she stumbled over basic policy questions and left open the possibility that she would cut education funding, privatize public schools and scale back the Education Department’s civil rights work.

[The popular uprising that threatens the Betsy DeVos nomination]

Video clips from that hearing went viral, and DeVos became an instant meme just days before Trump’s inauguration. Opposition to her nomination then rode a wave of anti-Trump momentum after the Women’s March on Washington.

“Across the country parents, teachers, community leaders and civil rights advocates are rightly insisting that the federal role in education should be to strengthen public education, not abandon it, and to protect students’ civil rights including students with disabilities, low-income students, students of color, LGBT students, and immigrant students,” King said. “The open question now is, will the future leadership of the department heed that message?”

It remains to be seen whether the pushback against DeVos across the country and on Capitol Hill would affect her ability to advance her agenda in office. She has promised that she would not force vouchers onto states that don’t want them, but she has also said that she continues to think that it’s important for parents to have the opportunity to choose alternatives to traditional public schools — including vouchers, full-time virtual schools and public charter schools.

Trump has pledged to redirect $20 billion in federal funds to an effort to expand school voucher programs and charter schools. This proposal, which would require congressional approval, seemed a heavy lift even before the resistance to DeVos’s nomination.

There also has been speculation that the Trump administration may seek to promote private-school choice in a broad overhaul of the tax code, or through a competitive grant program such as Obama’s Race to the Top, which helped persuade states to adopt Common Core academic standards and new teacher evaluations in return for a better shot at federal dollars.

Some Republicans hope that, with Trump and DeVos in office, they would be able to win a fight they have lost repeatedly in recent years: Allowing $15 billion in Title I funds, meant for the education of low-income children, to follow students to the schools of their choice, including private schools.

There are plenty of priorities DeVos could push with executive power, including rolling back or revising Obama administration guidance on how schools handle complaints of campus sexual assault and what accommodations they must make for transgender students. The agency also has wide latitude to decide how aggressively to investigate complaints about civil rights and special-education services, and it is responsible for deciding whether state plans for judging the success of schools measure up to the law.

[Democrats speaking for 24 hours in last push against DeVos]

Democrats argue that the uprising against DeVos would hamper her ability to lead. Sen. Patty Murray (D-Wash.), the ranking Democrat on the Education Committee, said Monday that DeVos would be “the most controversial and embattled” secretary in the history of the department.

“She would start this job with no credibility inside the agency she is supposed to lead. With no influence in Congress. As the punchline in late-night comedy shows — and without the confidence of the American people,” Murray said near the start of a 24-hour Democratic speech-a-thon against DeVos, a last-ditch effort to derail her confirmation.

The committee’s chairman challenged Democrats to find common ground with DeVos. “For the last eight years I worked well with President Obama’s Education, Health and Energy secretaries, and the president himself, even though we had fundamental disagreements on the federal role in education, Obamacare and energy policy,” Sen. Lamar Alexander (R-Tenn.) said.

Sen. John Cornyn (R-Tex.), the majority whip, praised Trump 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.”

Throughout Donald Trump’s campaign and now into the first weeks of his presidency, critics suggested that he cool his incendiary rhetoric, that his words matter. His defenders responded that, as Corey Lewandowski said, he was being taken too “literally.” Some, like Vice President Pence, wrote it off to his “colorful style.” Trump himself recently explained that his rhetoric about Muslims is popular, winning him “standing ovations.”

No one apparently gave him anything like a Miranda warning: Anything he says can and will be used against him in a court of law.

And that’s exactly what’s happening now in the epic court battle over his travel ban, currently blocked by a temporary order set for argument Tuesday before a three-judge panel of the U.S. Court of Appeals for the 9th Circuit.

The states of Washington and Minnesota, which sued to block Trump’s order, are citing the president’s inflammatory rhetoric as evidence that the government’s claims — it’s not a ban and not aimed at Muslims — are shams.

In court papers, Washington and Minnesota’s attorneys general have pulled out quotes from speeches, news conferences and interviews as evidence that an executive order the administration argues is neutral was really motivated by animus toward Muslims and a “desire to harm a particular group.”

His words, the two states say in their brief, show “that the President acted in bad faith in an effort to target Muslims.” The courts, they say, “have both the right and duty to examine” Trump’s “true motives.”

The states offer a multitude of exhibits, starting with a December 2015 release from the Trump campaign calling for a “total and complete shutdown of Muslims entering the United States until our country’s representatives can figure out what is going on.”

They cite his August speech advocating screening out people “who believe that Sharia law should supplant American law.”

Another exhibit: His Jan. 27 interview with the Christian Broadcasting Network in which he said he wanted to give priority to Christians in Syria.

They even hauled out Rudolph W. Giuliani’s comment on Fox News that Trump wanted a “Muslim ban” and requested he assemble a commission to show him “the right way to do it legally.”

In response, government lawyers are trying to have Trump’s rhetoric treated, so-to-speak, as inadmissible and irrelevant. It is inappropriate and contrary to precedent, they say in their brief, for the court to “’look behind’ the stated basis for the Order to probe its subjective motivations.” The states, they complain, are asking “the courts to take the extraordinary step of second-guessing a formal national security judgment made by the President himself pursuant to broad grants of statutory authority.”

How the appeals court and ultimately, no doubt, the Supreme Court, responds remains to be seen. Both sides have their precedents to cite on probing presidential motive.

And there are numerous other issues in the case, including the government’s argument that the states do not have standing to sue. If the appeals court and the Supreme Court agree, this particular case could come to an abrupt halt without a decision on whether Trump’s order violates anyone’s rights under the Constitution.

However it comes out, it may or may not sink in with Trump that his words can be used to wreak havoc with his policy agenda.

His remarks could hurt the government’s key argument as it seeks to reinstate the order — that there was a “rational basis” for issuing it — said Jayashri Srikantiah, an immigration law professor at Stanford Law School.

“When there is a record of evidence, as there is here, of the president making discriminatory comments about Muslims, the question is, does that animate the executive order?” Srikantiah told The Washington Post. “If it does, it raises some serious concerns and it reflects an intentional discrimination.”

“It’s pretty unusual for a president to make those kinds of statements so candidly or publicly,” she continued. “In some ways, this is new territory.”

Trump’s call for a Muslim ban came just days after the deadly terrorist attack in San Bernardino in 2015, in which a Muslim couple shot and killed 14 people and injured 22 others at a holiday party. In December, during an appearance on ABC’s “Good Morning America,” Trump suggested that the proposed ban was “no different” than President Franklin Roosevelt’s internment of hundreds of thousands of Japanese Americans during World War II.

Trump again called for a “ban” after the Pulse nightclub shooting in June, the deadliest mass shooting in U.S. history. He framed the attack as an immigration issue, even though the shooter was a U.S. citizen born in New York to Afghan parents. The ban, Trump said in a speech in New Hampshire, would be lifted “when we as a nation are in a position to properly and perfectly screen” people entering the country.

“We are importing radical Islamic terrorism into the West through a failed immigration system,” he said. “If we want to remain a free and open society, then we have to control our borders.”

The plan seemed to shift later in the summer, when Trump said he intended to suspend immigration from “any nation that has been compromised by terrorism.” When asked in an appearance on “Meet the Press” in July if the change marked a “pull-back on his Muslim ban,” Trump responded that it didn’t, saying it could be viewed instead as an “expansion.”

In a foreign policy speech the following month, Trump proposed an ideological test for new immigrants, saying government should screen out any travelers “who believe that Sharia law should supplant American law.” He seemed to temper his remarks as the election drew closer, calling for “extreme vetting” of people entering the country as opposed to an outright ban. But late last month, in an interview with the Christian Broadcasting Network, Trump said he wanted to give priority to Christian refugees over Muslims fleeing conflict in the Middle East.

All this and more have been submitted as exhibits in the case to illustrate that the travel restrictions aren’t what the administration claims in court: A lawful “exercise of the President’s authority over the entry of aliens into the United States and the admission of refugees” that is neutral on nationality or religion, based not on any hostility toward Muslims but on a congressional determination of countries that are hotbeds of terrorism.

It is unknown what advice President Barack Obama gave to President Trump in the traditional letter left in the Oval Office on Inauguration Day. But he could have given Trump a lesson in how words come back to haunt presidents, as that’s exactly what happened to Obama in his own immigration case when it reached the courts.

When Texas and 25 other states successfully sued to temporarily block Obama’s attempt to shield millions of illegal immigrants from deportation in 2015, among their chief arguments was that the president’s executive actions were an overreach, an end-run around the Republican-controlled Congress that had refused to go along with his proposals.

Among their best pieces of evidence were some of Obama’s own words, uttered at a moment of frustration when he was getting heckled for his deportation policy: “… I just took an action to change the law,” he responded.

Both the U.S. district court and the 5th U.S. Circuit Court of Appeals used those and other words against him when they ruled against Obama.

When the Supreme Court deadlocked in the case, the lower court decisions stood.

It was, as The Post’s Robert Barnes reported in June 2016, “the biggest legal defeat of his administration.”