"Sign, sign, everywhere a sign — blockin' out the scenery, breakin' my mind." Apologies to the Five Man Electrical Band and its 1971 hit song, but campaign Sard signs are sprouting like weeds in this particularly polarizing election cycle. With them have come vandals carving Trump signs into "Rump" signs, and vigilantes defying local ordinances to festoon their properties with dozens of partisan placards. How is it that these analog expressions of political...