Republican Maine Sen. Susan Collins faces a high-stakes test with an obvious answer: Education Secretary-designate Betsy DeVos has been hostile to the nation’s public schools even as she’s demonstrated no grasp of the issues facing them, so she shouldn’t have a role in the nation’s largest public education agency.

DeVos cleared a big hurdle Tuesday when her nomination was sent to the full Senate for a confirmation vote. Now Collins, who voted for DeVos in committee, says she hasn’t decided whether she’ll support DeVos on the Senate floor. Independent Maine Sen. Angus King has already come out against DeVos. But Collins, considered a moderate in Washington, could be a swing vote: Republicans have a 52-48 edge in the Senate, meaning that every Democrat and three Republicans would have to vote against DeVos for the nomination to be rejected.

One of the first Republicans to express reservations about President Donald Trump’s education nominee, Maine’s senior senator said that DeVos’ awkward Jan. 17 confirmation hearing left her concerned about the nominee’s “apparent unfamiliarity with” the Individuals with Disabilities Education Act, which requires states to provide free and appropriate education to children with disabilities.

Asked by Sen. Tim Kaine, D-Va., whether all schools that get federal funding should have to abide by the federal civil rights law, DeVos replied, “I think that is a matter best left to the states.” It’s not clear whether she actually doesn’t understand IDEA or doesn’t believe that federal statutes should take precedence over states’ rights. Either should raise eyebrows.

More worrisome is DeVos’ activism on behalf of school choice. Collins says that she’s been assured that, if confirmed, DeVos would not push school vouchers on states by tying federal funding to the presence of state voucher programs. But the nominee — a billionaire philanthropist — chairs a Washington nonprofit that favors the use of taxpayer dollars to pay for private and parochial schools, and it’s hard to imagine her forfeiting an opportunity to turn her values into policy.

In her home state of Michigan, DeVos proposed an amendment to the state constitution that would have cleared the way for public funds to be used to pay for private and religious education. The state’s voters overwhelmingly rejected the 2000 proposal, but Betsy and Richard DeVos bounced back, funding successful efforts to lift a cap on the number of charter schools in Michigan and defeat measures providing for public oversight of charters.

Thanks to the DeVoses, according to Politico Magazine’s Zack Stanton, about 240 of Michigan’s 300 publicly funded charter schools are run by for-profit companies. “This means that taxpayer dollars that would otherwise go to traditional public schools are instead used to buy supplies such as textbooks and desks that become private property,” Stanton wrote.

DeVos demonstrated her intransigence on the topic at her Jan. 17 confirmation hearing. Repeatedly asked by Tim Kaine whether all federally funded schools — public, public charter or voucher-funded private institutions — would be held to the same standards of accountability, the nominee refused to be pinned down. (What’s more, reported Politico’s Stanton, most of Michigan’s loosely overseen charters “perform below the state’s averages on tests.”)

In a nation where the overwhelming majority of students attend public schools, DeVos is out of touch with the concerns of millions of American families. The idea of her helping shape national education policy is alarming, and Susan Collins should step up and help stop DeVos in her tracks.