It was unclear if the arrest would force Gordillo out of her union leadership position. Mexican mining union boss Napoleon Gomez Urrutia has continued to hold his post more than four years after he moved to Canada amid accusations that he misappropriated $55 million in union funds.
Many Mexicans immediately began suggesting prosecution of other union leaders. Opposition parties mentioned the boss of the oil workers union, Carlos Romero Deschamps, who, according to Mexican news media, gave his son a $2 million Ferrari and whose daughter posted Facebook photos of her trips to Europe aboard private jets and yachts.
Romero Deschamps' immunity from prosecution as a legislator — a status he still enjoys — helped keep him from going to jail in a scandal over his union's illegal $61.3 million campaign donation to the PRI in 2000.
But if Deschamps stayed within the womb of the PRI while under fire, Gordillo was unusually defiant, allying at times with presidents from the National Action Party, helping create a new political party and finally bolting from the PRI, where she had long been an influential figure. Many credited her party with pulling enough votes to swing the narrow 2006 election to National Action's Felipe Calderon.
Sergio Aguayo, a political analyst at the elite Colegio de Mexico, said Gordillo "wasn't just a shadow power, but one that wanted to be a political power."
"In Pena Nieto's vision of Mexico, no one can be above the president," Aguayo said. "It's the same old imperial presidency."
Gordillo's combativeness may have led her to miscalculate Pena Nieto's willingness to reinstate the old tradition of unquestioned presidential authority.
"She underestimated him," columnist and political analyst Raymundo Riva Palacio said of Pena Nieto.
The PRI, which ruled Mexico from 1929 to 2000, spent 12 years out of power before returning to the presidency with Pena Nieto's 2012 election victory.
Gordillo's arrest recalled the 1989 detention of once-feared oil union boss Joaquin Hernandez Galicia. He had criticized the presidential candidacy of Carlos Salinas and threatened a strike if Salinas privatized any part of the government oil monopoly.
On Jan. 10, 1989, about a month after Salinas took office, soldiers used a bazooka to blow down the door of Hernandez's home in the Gulf Coast city of Ciudad Madero.
He was freed from prison after Salinas left office.
Salinas' sweep of old, uncooperative union bosses also led to opening the way for a new, up-and-coming leader in the teachers union, Gordillo, who was at first seen as a reformer.
Gordillo's arrest alone is far from enough to help Pena Nieto improve Mexico's schools. So great is the union's control over hiring that even the government acknowledges it's not sure how many schools, teachers or students exist in Mexico.
The Mexican education system has been persistently one of the worst performers among the world's developed economies, with few signs of improvement. Nearly every Mexican 4-year-old is in pre-school, but only 47 percent are expected to graduate high school. In the U.S., the number is closer to 80 percent.
In a television interview last week about education reform, the interviewer told Gordillo that she was the most hated woman in Mexico.
"There is no one more loved by their people than I," Gordillo answered. "I care about the teachers. This is a deep and serious dispute about public education."
Union leaders voiced support for her during a meeting in Guadalajara but issued no formal statement and there were no public demonstrations by teachers.
"To our leader, teacher Elba Esther Gordillo, we affirm our loyalty, our love and our solidarity," Juan Diaz de la Torre, the union's general secretary, said during the meeting.
Associated Press writers Olga R. Rodriguez, Adriana Gomez Licon and Michael Weissenstein contributed to this report.