Betsy DeVos’s confirmation as education secretary is all but assured after an unusual and contentious early-morning vote by the U.S. Senate.

The Senate convened at 6:30 a.m. Friday to “invoke cloture” on DeVos’s embattled nomination, a move meant to end a debate that has grown unusually pitched both within the lawmaking body and in the wider public.

They voted 52-48 to advance her nomination, teeing up a final confirmation vote by the end of the day Monday.

Two Republican senators who said earlier this week that they would not vote to confirm DeVos joined their colleagues in voting to allow a final vote on Monday. Susan Collins of Maine and Lisa Murkowski of Alaska cited DeVos’s lack of experience in public education and the knowledge gaps she displayed during her confirmation hearing last month when announcing their decisions and each said feedback from constituents had informed their decisions.

Americans across the country have been flooding their senators with phone calls, faxes, and in-person visits to share opposition to DeVos, a Michigan philanthropist who has been a leading advocate for school vouchers but who has never worked in public education.

They are likely to keep up the pressure over the weekend and through the final vote, which could be decided by a tie-breaking vote by Vice President Mike Pence.

Two senators commented on the debate after the vote. Republican Lamar Alexander of Tennessee, who has been a leading cheerleader for DeVos, said he “couldn’t understand” criticism of programs that let families choose their schools.

But Democrat Patty Murray of Washington repeated the many critiques of DeVos that she has heard from constituents. She also said she was “extremely disappointed” in the confirmation process, including the early-morning debate-ending vote.

“Right from the start it was very clear that Republicans intended to jam this nomination through … Corners were cut, precedents were ignored, debate was cut off, and reasonable requests and questions were blocked,” she said. “I’ve never seen anything like it.”