Maine’s senior U.S. senator, Republican Susan Collins, said Wednesday that she will oppose President Donald Trump’s pick for secretary of education.

In a move praised by the Maine Education Association, Collins said she cannot vote for Betsy DeVos for the post because she’s concerned the nominee doesn’t have enough familiarity with the needs of public education.

Maine’s other U.S. senator, independent Angus King, has already said he won’t endorse DeVos.

It isn’t clear whether DeVos can muster a majority in the Senate, which has 52 GOP members. Because Vice President Mike Pence can break a tie, she needs to secure the backing of 50 senators.

At least one other Republican, Alaska’s Lisa Murkowski, also said she will oppose DeVos. But she may be the only other Republican to side with Collins.

Sean Spicer, the White House press secretary, said during a briefing that he is “100 percent confident” that DeVos “will be the next secretary of education.”

Collins said her choice to cast a vote against DeVos is “not a decision that I have made lightly.”

She said she has no doubt DeVos cares about children and she appreciates how much time and attention the nominee has devoted to helping at-risk children over the years with her work on charter schools and voucher programs.

“She appears to view education through the lens of her experience of providing alternatives to public education,” Collins said.

Lois Kilby-Chesley, president of the MEA, called it refreshing “to see a lawmaker who is willing to listen to educators, the experts in the classroom, when it comes to key decisions concerning our students and the profession.”

She said many of the organization’s 23,000 members emailed, wrote personal letters and phoned Collins until her lines jammed to ask her to oppose DeVos.

“Sen. Collins took the time to listen and make a thoughtful decision, one that in the end is in the best interest of Maine students,” Kilby-Chesley said.

Supporters argue that DeVos has spent her career fighting for better education for students who are often stuck in poor public schools. As the leader of the American Federation for Children, an organization whose mission is to improve K-12 education in ways that empower low-income parents, she won accolades from supporters as diverse as former first lady Barbara Bush and former Democratic vice presidential candidate Joe Lieberman.

Critics say she is not qualified, is too attached to private school alternatives and is only under consideration because she’s been a big donor to the GOP for years.

Democrats, who need at least three GOP votes to block any Cabinet nominee, are trying to stop some of the most highly visible nominees, including DeVos, who is strongly opposed by teachers’ unions and many public school officials around the country.