One month ago (or an eternity in politics), Obama and Clinton got into a spat over Ronald Reagan and his ideas. While the rival campaigns argued whether Reagan was actually a "transformative figure," they both agreed his ideas were bad. But now that the Democratic contest has started to turn nasty, it maybe time for the Democrats to remember Reagan's most important idea: "Thou shalt not speak ill of any fellow Republican."
Reagan's famous Eleventh Commandment has so far serviced his party well. When primary fights turn negative the result is usually bad for the party. Barry Goldwater in 1964, Hubert Humphrey in 1968, Jimmy Carter in 1980, and Walter Mondale in 1984 were all hurt by bitter primary battles.
The Democrats have a great chance of winning the presidency. The current Republican president and party have historically low approval ratings. Looking at primary turnouts and money raised, it appears the Democratic base is at an all-time high level of excitement. But the Democrats haven't won the presidency yet. Whoever the nominee is will be up against John McCain, a very formidable opponent. If the primary continues to get more negative, the Democrats may yet snatch defeat from the jaws of victory.