The nomination fight over Betsy DeVos has triggered a record number of calls to the U.S. Capitol switchboard, according to lawmakers — and they say it’s working.

The U.S. Senate voted unusually early Friday to advance the nomination of President Donald Trump’s choice for education secretary, who Senate Minority Leader Chuck Schumer described as “one of the worst nominees that has ever been” chosen.

The full vote is expected Monday, and senators expect to get an earful from their constituents over the weekend.

A spokesman for Schumer said the Senate had been flooded with an average of 1.5 million calls a day this week, and Sen. Brian Schatz (D-HA) said Thursday that the previous three days had been the “busiest in Capitol switch board history, by almost double.”

The last three days have been the BUSIEST IN CAPITOL SWITCHBOARD HISTORY. By almost double. This is working. Keep it up and please RT.

— Brian Schatz (@brianschatz) February 2, 2017

Schatz and Sen. Cory Booker (D-NJ) agreed the calls were working, and invited more callers to oppose the billionaire Republican campaign contributor.

Some of their GOP colleagues are feeling the heat, and their constituents have complained they were unable to reach their senators to urge them to vote against DeVos.

But Sen. Lisa Murkowski (R-AK) said the calls had led her to vote against DeVos, and she was joined by Sen. Susan Collins (R-ME).

GOP Sen. Lisa Murkowski says constituent calls to her office against DeVos were a major reason why she is voting against her nomination

— Miranda Green (@Mirandacgreen) February 1, 2017

Teachers unions and progressive activists kicked off the fight against DeVos, but the campaign quickly became grassroots.

“What we really see is that this has really touched a nerve in the hearts and minds of not just educators but parents, grandparents and community members,” said Mary Kusler, director of government relations for the National Education Association.

Callers are troubled by her longtime support for private school vouchers and total lack of experience with public schools as a professional, parent or student.

Others are concerned that DeVos appears unwilling to enforce the federal Individuals with Disabilities Education Act, which requires states and school districts to provide a free public education to about 6.5 million students with disabilities.

“She didn’t seem to understand that the federal law is the only thing that truly ensures children with disabilities a free and appropriate education,” said Amy Boyne, an Ohio mother who has called her own senators and others. “Yes, there is a lot of fear in the disability community. I just cannot believe someone with her lack of qualifications is going to have so much power.”

The teachers union also reported more than 1 million emails opposing DeVos had been sent through its online form to lawmakers, which nearly quadruples the previous record of 284,000.

With the defections of Murkowski and Collins, DeVos’ confirmation vote is now split 50-50, which would require Vice President Mike Pence to cast the tie-breaking vote in history for a presidential nominee.

The last cabinet nominee to be defeated by senators from the president’s own party was in 1925, when Calvin Coolidge’s attorney general nominee, Charles B. Warren, was rejected in the wake of the Teapot Dome scandal.