Stop Sign with Santorum bumper sticker. Near a Wegmans supermarket, State College, Pennsylvania, January 2016.
"Stop War" poster, silk screen, Berkeley, California, c. May 1970, from Thomas W. Benson Political Protest Collection, Special Collections, Penn State University Libraries and Thomas W. Benson, Posters for Peace: Visual Rhetoric and Civic Action (University Park: Penn State University Press, 2015).
When is the last time you saw a STOP sign decorated with an addition that constituted it as a political slogan? The "Stop War" poster shown above was part of the peace movement at the University of California, Berkeley, in May 1970, after the Cambodia invasion and the shootings at Kent State. Did the poster prompt others to add words to STOP signs, or was the poster artist inspired by a practice that was already ongoing? I can't remember, though it seems to me I saw STOP WAR on public STOP signs around the country at about that time, and perhaps before.
The STOP SANTORUM sign in the photograph above refers to and is a relic of the presidential primary campaign of 2012, and it was still there this week when I took the photograph -- January 2016.
It seems to me that the tone of these STOP WAR alterations was at the time somewhat transgressive, suggesting not only an appeal to peace but an act of resistance by defacing what is, after all, government property and a sign of government's regulative power. As the years have gone by, that cluster of rhetorical suggestions seems to me to have dimmed somewhat, with the worldwide spread of graffiti. Altering a STOP sign is still illegal, and so still formally an act of resistance or at least of exclamatory, even imperative, appeal, but the power has been diluted by use and context. STOP sign defacements are no longer the property of the Left, though probably most of such uses are anti-establishment in context and appeal. One has often seen, for example, Ron Paul, and now Rand Paul defacement of traffic signs. Are we all anti-establishment now?
See also http://nyti.ms/1Lrhss3 "Why Can't the GOP Stop Trump?" March 3, 2016.