Success Academy CEO Eva Moskowitz, the divisive charter school chief who has frequently clashed with Mayor Bill de Blasio and has long expressed an interest in running for mayor, will make an announcement Thursday at City Hall about her “political plans,” a spokesman said.

As head of the city’s largest charter school network whose students consistently outscore most of their charter and traditional school peers on state tests, Moskowitz is a lightning rod in education debates in New York and beyond — lionized by charter school proponents as a fierce advocate for the movement, but villainized by teachers unions as an enemy of their members and public education writ large.

Word of the announcement came Wednesday afternoon after thousands of charter school supporters marched to City Hall, including parents, students, and teachers from Success’ nearly three-dozen schools. The rally was organized by Families for Excellent Schools, a powerful lobbying group with close ties to Success, which has waged an expensive publicity campaign against de Blasio’s education agenda and his union allies.

Moskowitz, who previously served alongside de Blasio on the City Council, has engaged in repeated high-profile tussles with him since he became mayor. She defeated him early in his tenure when he tried to block her schools from moving into public buildings, and she has more recently publicized their disputes over payments and public space for her schools.

Richard Millett, who described himself as a part-time “administrative assistant to Eva with political matters,” sent the notice to reporters about Thursday’s announcement. He said the announcement would concern “her personal political realm,” and would not relate directly to Success. He added that his full-time job is a legal assistant at the firm of Eric Grannis, Moskowitz’s husband.

Joseph Viteritti, a public policy professor at Hunter College, said it would be very early for any candidate to declare their intention to compete in the 2017 mayoral elections. He added that most New York City mayors who run for a second term are re-elected, and noted that de Blasio has broad support among politically potent labor groups.

“He’s at a great advantage,” Viteritti said.