That's a great point. I hadn't heard about the Boilermakers, but all the police and firefighter unions are endorsing Trump. Union members are roughly 50/50, but leadership is almost exclusively Dem. Until now. Not nearly as much union $$ and pavement pounding going for the Dems this election. That affects races lower down the ballot.
As an aside, a friend works for a NY state agency, Conservative as can be. She was appointed union shop steward, since no one wanted it, a couple of years ago. She alerts other conservatives to volunteer as spots opens. Now 6 out of 30ish shop stewards are good guys.