It's a forthright, not too subtle, attempt to divide the union movement.  Under George Meany (circa 1970) the AFL-CIO was BFF with Republicans.  Richard L. Trumka, the current president, has been singing a vastly different tune.

If people voted for their own self-interest, Republicans would get about 3% of the vote, Democrats would get about 30%, and "other" would pick up the rest.
Disclaimer: I'm just pulling those numbers out of the air, but it's hard for me to imagine anyone who actually works for a living having a good reason to vote Republican.  It's hard for anyone who would like something resembling civilization to exist in 50 years to justify such a self-destructive act.