The Democrats have played it safe for a generation. Both as the insider party and as the outcast party, through the 2004 election the Democrats played it safe with their presidential candidates. The last succesful Democratic candidate, Bill Clinton, was notable mostly for the fact that he governed from the center and while his legacy was good for America he did not bring his party any national success. Both Gore and Kerry were good guys (I have a significant amount of affection for Al Gore, but I have been a Gore fanboy since 1988 - I'm weird that way) but neither was the sort of game-changing pol like Kennedy, Reagan or Bush II. Of course, in the case of Reagan and Bush II, it's clear that being a game-changer is not always for the best.
In 2008 Democrats see a very vulnerable post-Bush Republican party as well as a nation primed to vote in a new Democratic president. As E.J. Dionne points out, this has presented something of a predicament especially for Sen. Clinton. If we're going to have a Democratic president, shouldn't it be someone that won't play safe like the ball-control offense of Marty Schottenheimer (Martyball) but instead someone who will air it out like Air Coryell or the Rams of '99-01?
We played it safe for a long time, and sometimes it got the most votes (Clinton, Gore) and sometimes it didn't (Kerry, Dukakis, Mondale). It's almost like we've gotten the ball to the 1yd line, and sure we could kick the field goal on fourth down for a safe three points... but why not hand the ball to our ace running back and bust right through to the end zone?
ALSO: OMG, six months until football? Are you kidding me?