I have a theory that the party out of power tends to be more crackpot then the one in power.
Well, that's easily debunked... do you really think that the dems were more crackpot than the shrub during his time in office?
Please note also... Dems do not engage in groupthink the way the republicans do. Looking at the actual votes shows that the democrats split their votes to a much greater degree than the republicans... in other words, evidence of actually having a personal opinion and voting their conscience, rather than merely spewing a bunch of hateful rhetoric about how bad government is and toeing whatever party line they are forced to adopt to get the paranoids fired up enough to show up at the polls.
To me the current defining difference between the parties is that dems tend to think that it is OK to disagree and have differences while Republicans want everyone to gravitate toward the loudest and most listened to voices of a vigilante mob.
You don't have to be an animal rights activist, a vegetarian, an alarmist tree hugger, or a legalized pot advocate to be a liberal dem. Liberalism has many forms which are often in disagreement with each other.
On the Republican side there is much less disagreement in voting patterns, and they are also much more susceptible to the popular political trends of the time... such as the tea party movement.
There are reasons for this effect. Conservatism suggests unity and stability of culture and a resistence to change. That which is unfamiliar and different must be opposed. This also suggests that we must be more similar to each other in our opinions, our rituals, and our values than what we actually are.
Liberalism wants progress. We can progress in many different directions. There is historically no need nor desire for a contract for or on America on the liberal side of the house.