The American Federation of Teachers backed Democrat Hillary Rodham Clinton's presidential bid on Wednesday.

The 1.4 million-member union said it would immediately begin a program to mobilize voters in support of Clinton across the country. AFT represents school employees including teachers in pre-kindergarten through 12th grade and has more than 3,000 local affiliates and 43 state affiliates. It is an affiliated international union of the AFL-CIO.

The union's executive council chose the New York senator after meeting with seven Democratic candidates. No Republican candidates accepted the union's invitation to participate in the process.

AFT President Edward J. McElroy said members chose Clinton not only for her stance on education, but also health care and her "long, established record on the issue."

He noted that she had been working on education since she was the first lady of Arkansas and was appointed by her husband to head the school reform effort. He didn't mention that she had sparred with teachers' union officials back then for supporting a teacher-testing proposal that the unions opposed.

McElroy said that the decision to endorse Clinton was not because her rival Barack Obama has been on the campaign trail promoting performance-based merit pay for individual public school teachers. Teachers frequently say that linking their pay to their students' test scores can be unfair to those instructing kids from disadvantaged backgrounds. AFT's leaders say performance pay should be bargained locally and isn't an issue for national politics.

Clinton, speaking to reporters during the announcement, said she supports another version of merit pay, one that may be more palatable to unions.

"I have supported school wide pay for performance programs because I think that the school has to be viewed as a whole unit with everybody working together," she said. "I'm a strong believer that we've got to be creative and innovative in how we help teachers do what is a very difficult job."