Cynthia Nixon is calling on lawmakers to immediately repeal New York’s unpopular teacher evaluation law, catapulting her gubernatorial campaign into one of the messiest debates in New York state education policy.

Nixon called on her Democratic primary opponent Gov. Andrew Cuomo to stop making “excuses” about the law that he once championed, which has faced significant pushback for the way it tied educator ratings to standardized test scores and was later put partially on hold. The former “Sex and the City” star’s plan received support from a group of a few dozen education leaders called “Educators for Cynthia,” which includes education historian and testing opponent Diane Ravitch.

The announcement puts Nixon on board with the state’s teachers union agenda and threatens to drive a wedge between Cuomo and the major labor group, which he’s had a tenuous relationship with in the past.

“A couple years ago Andrew Cuomo described teacher evaluation based on high stakes testing as one of his greatest legacies, now he is hoping that parents and teachers have forgotten all about it,” Nixon said in a statement released on Thursday. “Enough of the delays and excuses Governor Cuomo, it is time to repeal the APPR now.”

In a statement, a Cuomo campaign spokeswoman attempted to distance the governor from the issue of teacher evaluations, instead turning the blame on the education department.

“Experts across the board agreed that the implementation of Common Core was botched by SED, which is why they have been tasked to overhaul it and the Board of Regents adopted a moratorium on the use of tests in the evaluation,” said Cuomo campaign spokeswoman Abbey Fashouer.

But it was Cuomo who led the charge to create a new teacher evaluation system in 2015, even calling the old system “baloney” in his State of the State address that year. The measure he fought for passed — allowing half of an individual educator’s rating to be based on test scores — but not without a fued with the unions.

Since then, Cuomo has done an about-face on education policy, leading to a friendlier relationship with the labor groups. The governor has also been courting organized labor this year by standing up for union protections in the face of a Supreme Court case that could hinder the union’s ability to collect fees. Both state and city teachers union leaders said earlier this year they had begun to set aside their differences with the governor and were pleased with his new direction.

But the call to repeal New York’s teacher evaluation law has been a major priority for the state teachers union this year. Officials at the New York State United Teachers have been out on a limb calling for an immediate law change that would allow local districts to craft their own evaluation systems. Their push, however, has gained little traction from lawmakers or officials at the state education department, who are trying to revamp teacher evaluations through a slower process.

“First and foremost, the teachers that we represent believe that the time to fix [teacher evaluation] is this year,” said Jolene DiBrango, executive vice president of NYSUT, during a February Board of Regents meeting. “Now is the time — we’ve been talking about this for years.” (Neither the state or city teachers unions responded to immediate request for comment on Thursday.)

Crucial aspects of the evaluation system that Cuomo championed three years ago are currently on hold. After a spate of education issues — including the teacher evaluation system — caused a statewide testing boycott, the governor began reexamining some of his education policies..

Cuomo appointed a task force to review state learning standards that eventually called for a freeze on the use of test scores in teacher evaluations. The state’s Board of Regents soon obliged, placing a moratorium on the use of grades 3-8 math and English tests in teacher ratings until 2019. But the law remains on the books, and state officials are just starting to dive into the issue again as the moratorium nears its end.

Officials from Nixon’s campaign said that she believes evaluations should be locally designed and that high-stakes tests should not be used to judge teachers.

This story has been updated to include information from Nixon’s campaign on her vision for teacher evaluations.