The hashtag #CharacterstoSpare shot up in usage after 1 p.m., according to analytics by Topsy. The phrase was initially mocked by Romney supporters and anti-Obama conservatives, but quickly became a battleground for supporters on both sides, with the Democratic National Committee and Obama for America campaign workers jumping on Obama's Romney attack line.

Hashtags have become the new way to watch political battles play out through the digital space, and conservatives have become particularly adept at appropriating them to mock the other side. But hashtag campaigns — accidental or on purpose — remain at least temporarily effective for publicity and raising awareness.

"When your hashtag is taken over by the other side ... at the end of the day they're having real conversations on your turf,"  National Republican Congressional Committee Digital Director Gerrit Lansing explained to ClickZ last week.

—Amie Parnes contributed.