The provenance of the meme was unclear. It was most likely intended merely as a joke, which one side then interpreted as a genuine attempt to suppress Democratic voter turnout in Pennsylvania, and which the other side claimed was spread as a smear against their candidate by suggesting his party would resort to such underhanded tricks. (Of course, it would be ridiculous to think that any particular online voting system could be used only by supporters of one particular candidate.)
Update: Looks like at least one local Republican official has circulated this, but we don’t know the origin.