From NBC's Domenico Montanaro
At 1 p.m., Clinton will be endorsed by the 1.4-million-member American Federation of Teachers.
The endorsement comes after votes from the 41-member AFT executive council and feedback from members through its Web site.
"Our members have told us that they want a leader they can trust to strengthen public education, increase access to healthcare, promote commonsense economic priorities and secure America's place in the world," said AFT President Edward J. McElroy in a press release. "Hillary Clinton is that leader."
***UPDATE*** NBC/NJ's Athena Jones adds the AFT chose to endorse Clinton after a seven-month process in which the union's executive council met with seven of the Democratic candidates and candidates participated in question and answer sessions with the council and with union members.