From a solid article from In These Times:
. . . .What makes union leaders' actions so astounding is that they rejected a stalwart champion [Bernie Sanders] of their agenda who raged against the billionaire class, walked picket lines with workers and spoke obsessively about widening inequality. Instead, they opted for a millionaire former Walmart board member with a checkered past on labor issues whose campaign refused to endorse a $15 minimum wage and couldn’t even muster a tweet in favor of low-wage workers.
Some union leaders’ sins are greater than others’. Randi Weingarten, president of the American Federation of Teachers (AFT), has long been engaged in what education scholar Lois Weiner has called a "public love fest" for the Clintons. As I noted recently, the AFT has given the Clinton Foundation somewhere between $1 million and $5 million under Weingarten for reasons that remain unclear. Her name was floated in some labor circles as a potential Clinton cabinet member.
In July 2015, AFT was the first national union to endorse Clinton—much earlier than the AFT had endorsed candidates in the past and likely over the objections of large numbers of its members who backed Sanders. From emails released by WikiLeaks, we know that Weingarten promised to act as an attack dog for Clinton against another union that had endorsed Sanders in the primary. . . .