“Don’t take union workers’ support for granted”
He’s warning about the rank-and-file; they helped deliver most of the upper Midwest to Trump.
Those union leaders are usually talking about the union money and endorsement they control while using the rank and file as proxy. However, if Trumka truly means the rank and file, he needs to look in the mirror because he and his fellow bosses are the ones alienating the rank and file by taking their money and throwing it at anyone sporting a D after their name.