At this point in the 1992 election cycle, the elder George Bush held an 89 a 66 percent approval rating (update: on October 13, 1991, according to Gallup data on the Roper Center website). Back then, Democratic figures including Mario Cuomo did not enter the 1992 race because they thought the elder Bush was “unbeatable” – just as today many Republicans are not entering the race, thinking Obama is unbeatable.
But Bush was defeated by Bill Clinton, who, a year before his victory, was a low-name-recognition outsider with personal baggage.
Clinton beat a popular incumbent with a fantastic approval rating. For the 2012 election, Barack Obama is just as vulnerable as the elder Bush, if not even more so. Obama currently has an approval rating of 23 percent. 40 percent (update: as of October 13-15, 2011, according to Gallup).
Upsets aren’t unusual. At this point in the 2008 election cycle, Hillary Clinton was viewed as having an insurmountable lead for the Democratic nomination. At this stage in 2004, John Kerry was thought to be running a vanity candidacy. By Election Day, a small swing in the Ohio count would have put Kerry into the White House. As for Ronald Reagan, at this point in the 1980 election cycle, he was the favorite to win the Republican nomination, but incumbent Jimmy Carter was expected to retain his post in the general election. Reagan ended up taking 44 states.