A new Gallup poll shows Barack Obama winning the union vote, 57%-35%, while Mitt Romney takes the non-union vote, 48%-44%.
Both government and non-government union workers deliver similar margins for Obama, while Romney holds his biggest lead (+6%) with workers who don't work for the government and aren't members of a union.
Here's the breakdown, via Gallup.
For historical context, this isn't an unusually large lead for Obama.
In 2004 exit polls, John Kerry beat George W. Bush with union members, 59%-40%, and in 2008, Obama beat John McCain, 61%-38%.
So relative to his GOP brethren, Romney (with his Bain Capital resume) isn't particularly strong or weak.