Every campaign has its boogeymen: those stock characters used by every politicians to embody the vague but malevolent forces that are coming to hurt you, the voter, unless you cast your vote for him or her.
The ultimate campaign boogeyman may have been Willie Horton, the Massachusetts prison inmate who was released on a furlough and went on to commit vicious crimes. In 1988, outside groups supporting then Vice President George H.W. Bush ran ads using Horton's bearded and menacing mug shot to bash Democratic candidate Michael Dukakis for backing the state's furlough program.
Dukakis, who was up nearly 20 points when the ads started running, has hardly been heard from since.
Boogeymen, though come in all shapes and sizes, and most aren't actual murderers. They just have to stand in for some social ill that the candidate vows to battle heroically on behalf of the voters.
Over time, you can watch the cast of boogeymen change along with the issues in play. As a handy guide, Politico compiled the boogeymen of the 2008 campaign, and a flashback to their 2004 counterparts. Don't be frightened.