Twenty-one Republican lawmakers have signed a letter that calls for a committee to investigate State Superintendent Ryan Walters and the Oklahoma State Department of Education.| MORE | Oklahoma Republicans call for investigation into Ryan WaltersThat committee could ultimately recommend that Walters be impeached. It is up to House Speaker Charles McCall to form that investigative committee. On Tuesday, he told his caucus that at least 51 Republicans need to sign on before he considers the request. "If they decide to move forward with that, it would be the most unprecedented move in state history to undermine the will of the Oklahoma voters," Walters said in response to the letter.The lawmakers allege failures to communicate with the legislature, not filling records requests, and not carrying out passed legislation.House Education Budget Chair Mark McBride, a vocal critic of Walters, cited a dispute over school security funding as the final straw."Among some of the other things, it’s just been a build-up over the last week or two," McBride said.McBride said he is not yet ready to say that impeachment is necessary, but that committee could take time to determine if it is warranted."They can decide is there an impeachable offense, or is there not an impeachable offense," McBride said.Walters remains defiant, accusing Republican lawmakers of teaming up with Democrats."These are folks that do whatever the teachers unions tell them to, and they want to bring back an era of the teachers unions controlling our schools," Walters said. “I will never back down to moderate Republicans partnering with Democrats to overturn the will of the people. We’re not going to allow it.” Melody Huckaby Rowlett, a political science professor at the University of Oklahoma, said House lawmakers don't need to prove a crime was committed if they were to impeach or have the Senate remove Walters from office. “What rises to level of impeachment is a little different. It’s broader. Alleged incompetence. Alleged willful neglect of duties. It doesn’t have to be high crimes and misdemeanors," Huckaby Rowlett said. The next step is to see if 30 more Republicans will sign the letter and if McCall will then assemble the committee. Top Headlines State Superintendent Ryan Walters responds to Republicans calling for impeachment investigation Investigation underway after deadly incident prompts heavy police response in southwest OKC Barack Obama is having a 'Brat' summer with Charli XCX on his summer playlist State Superintendent Ryan Walters, OSDE face pressure over open records delays Washing your fruits and veggies isn't enough anymore. Here's how to kill pesticides