Secret Service names, while irrelevant for the actual election, are always a good source for a little amusement. In 2007 Barack Obama was designated the "Renegade" as he sought to takedown "Evergreen"—the name given to Hillary Clinton back when she was first lady. Gerald Ford's "Pass Key" seemed to presage his early departure from the White House. George H.W. Bush's "Timberwolf" seems a little rough and tumble for the demure president. Personally I'm preferential to the evocative "Rawhide" that Reagan went by.
Now that Mitt Romney and Rick Santorum are being guarded by our nation's finest they've picked up new monikers for themselves. GQ nabbed the exclusive reveal last night. Romney will go by the handle "Javelin," one presumably directed to fell the incumbent president. For the few remaining months Santorum is in the race he'll be labeled "Petrus." The first results from Googling indicate that Petrus is Gordon Ramsey restaurant or a wine of the Bordeaux variety, but Santorum would never go by a term so sinful. No, his chosen name is of the divine nature, deriving from St. Peter, the first pope of the Catholic Church, just in case any voters have forgotten Santorum's strict religiosity.
As Marc Ambinder notes in the GQ post, these presidential nicknames are often meaningless. John McCain's "Phoenix" was randomly assigned when the last GOP candidate didn't want to pick one for himself. And while the code names were important during the age before encrypted communication, keeping the names secret serves no security purpose any longer.