A special prosecutor says then-Texas Gov. Rick Perry tried to force a Democratic district attorney to resign because he didn't approve of the "historical and current management decisions" of the public corruption unit she ran, according to a Friday court filing.

The Republican Perry was indicted in August by an Austin grand jury on felony abuse-of-power charges, but the latest paperwork sheds more light on the case against him should he go to trial.

The charges stem from Perry's 2013 publicly threatening, followed by the veto of $7.5 million in state funding for a public corruption division within the office of Travis County District Attorney Rosemary Lehmberg.

That came after Lehmberg, whose county includes Austin, rebuffed Perry's calls to resign following her drunken driving conviction.

"The state will prove that defendant Perry did not approve of historical and current management decisions regarding the operation of the Public Integrity Unit and therefore wanted to coerce Ms. Lehmberg into resigning her elected position and/or stymie or obstruct the continued operation of the Public Integrity Unit under Ms. Lehmberg's management," wrote the special prosecutor leading the case against Perry, Michael McCrum, in a filing signed by his assistant, David Gonzalez.

Perry left office last month after a record 14 years as Texas governor, but says he'll have an announcement on his expected run for the presidency in 2016 in May or June. Perry has long maintained that he was within his rights when issuing the veto and that he'd do it again if given the chance.

Perry's legal team tried repeatedly but unsuccessfully to quash the case on constitutional and technical grounds, and Perry has called it a political witch hunt. But Friday's filing suggests that the prosecution will argue that the then-governor was more interested in halting the work of the public integrity unit -- and Lehmberg's efforts overseeing it -- than the district attorney's drunken driving conviction.

The filing also complies with a previous order by the presiding judge, San Antonio Republican Bert Richardson, who suggested in a ruling allowing the case to continue last month that one of the criminal counts Perry faces was vague.

McCrum and Gonzalez made changes to more clearly spell out that as governor, Perry did not have direct governing authority over a local district attorney such as Lehmberg.

Perry is charged with abuse of official capacity and coercion of a public servant. If convicted, he could face up to 109 years in prison.