Emanuel faced an unwelcome political distraction as the walkout by 26,000 teachers and support staff in the third-largest U.S. school district forced hundreds of thousands of parents to scramble for a place to send idle children. The strike’s impact was sure to be felt nationwide in a year when labor unions have been losing ground across the U.S.

City officials vowed to protect nearly 350,000 students, acknowledging that children left unsupervised — especially in neighborhoods with a history of gang violence — might be at risk.

The two sides failed to reach a settlement after resuming negotiations Monday, extending the strike into at least a second day.

Chicago School Board President David Vitale said board and union negotiators did not even get around to bargaining on the two biggest issues, performance evaluations or recall rights for laid-off teachers. Chicago Teachers Union President Karen Lewis said that was because the district did not change its proposals.

“This is a long-term battle that everyone’s going to watch,” said Eric Hanuskek, a senior fellow in education at the Hoover Institution of Stanford University. “Other teachers unions in the United States are wondering if they should follow suit.”

Thousands of teachers and their supporters took over several downtown streets during the Monday evening rush. Police secured several blocks around district headquarters as the crowds marched and chanted.

The strike in Obama’s hometown quickly got caught up in election-year politics, as Republican presidential nominee Mitt Romney said Chicago teachers were turning their backs on thousands of students and accused Obama of siding with the striking teachers.

Obama’s top spokesman said the president has not taken sides but is urging both the teachers and the city to settle quickly.

The strike’s timing seems inopportune for Emanuel, a former White House chief of staff whose city administration was already wrestling with a spike in murders and shootings in some city neighborhoods before he agreed to take a larger role in fundraising for Obama’s re-election.

Emanuel and the union officials have much at stake. Unions and collective bargaining by public employees have recently come under criticism in many parts of the U.S., and all sides are closely monitoring who might emerge with the upper hand in the Chicago dispute as Election Day looms in November.

The union had vowed to strike Monday if there was no agreement on a new contract, even though the district had offered a 16 percent raise over four years and the two sides had essentially agreed on a longer school day. With an average annual salary of $76,000, Chicago teachers are among the highest-paid in the nation, according to the National Council on Teacher Quality.

But negotiators were still divided on job security measures and a system for evaluating teachers that hinged in part on students’ standardized test scores.

The strike in a district where the vast majority of students are poor and minority put Chicago at the epicenter of a struggle between big cities and teachers unions for control of schools.

Romney, who has been critical of public employee unions, said he was disappointed by the Chicago teachers’ decision to walk out of negotiations and sides with parents and students over unionized teachers, in a statement released Monday hours before he was set to land in Chicago for fundraisers.

Obama political aides in Chicago also criticized Romney for seeking political advantage and pointed to Romney’s repeated campaign statements that class sizes do not impact students’ education.

White House spokesman Jay Carney said Obama was monitoring the situation in his hometown but was not eager to take on a role in the dispute.

Some 140 schools were being kept open between 8:30 a.m. and 12:30 p.m. so the children who rely on free meals provided by the school district can eat breakfast and lunch, school district officials said.

The school district asked community organizations to provide additional programs for students, and a number of churches, libraries and other groups plan to offer day camps and other activities.

Union leaders said among the issues of concern was a new evaluation that would be unfair to teachers because it relied too heavily on students’ standardized test scores and does not take into account external factors that affect performance, including poverty, violence and homelessness. They said the evaluations could result in 6,000 teachers losing their jobs within two years.

City officials disagreed and said the union has not explained how it reached that conclusion.

Obama has urged accountability in teachers — moves that union leaders have opposed. For instance, Obama’s administration has favored pilot programs that challenge current practices, rewarding schools who try new approaches and has pushed for longer school days.

Obama’s education secretary, Arne Duncan, is a former head of Chicago Public Schools who pushed for changes that unions opposed.

___

Associated Press writers Tammy Webber and Don Babwin contributed to this report.