What does a union's endorsement mean? In PATCO's case, nothing. The Professional Air Traffic Controllers Organization found that out after it called a strike 1981. About 15,000 employees walked off the job -- illegally, because federal employees are forbidden by law to strike. Two days later, Ronald Reagan fired them, ushering in an era of defensive unionism that continues to today.
I have not found anything explaining why PATCO was one of a few unions to endorse Reagan in the 1980 election. But it started a trend of unions endorsing first and asking questions after the election.
Because the labor movement has seen such heavy setbacks, unions feel they need to "just get this person in office, then we'll be able to negotiate with them." That attitude destroys any perception of strength and dilutes the meaning of an endorsement until no one takes it seriously -- least of all the union members.
Unions need to stop offering candidates open wallets and phone banks. Unions instead need to ask candidates, "What's in it for us? What can you do for us?" There is no crime in reserving endorsement. If it is handed out rarely, and only to those who earn it, it gains power.