Supporters of Republican vice-presidential candidate, Alaska Gov. Sarah Palin cheer during a rally in Lancaster, Pa., Saturday, Oct. 18, 2008. (AP Photo/Matt Rourke)
Unless, I guess, they mean only one plumber's daughters. But you know they don't.
Fun fact: PSP's Sparklemom was a plumber's daughter!
UDATE/Correction: One of the plumber's daughters left a comment pointing out that the sign does, indeed, refer to one plumber, so the sign is correct. However, several misunderstandings and a lobbed "elitist" buzzword in the comment reveal that at least one of the plumber's daughters is a complete idiot.