A lot of the effort that has gone into analyzing the psychology of the Republican corruption machine and the Democratic failure machine seems to me to be missing a key point: each party's structure is floundering because it is in a position for which it wasn't designed. For forty years, the Republicans were the minority party, and their psychology, practices, and organization were designed with that in mind. Likewise, many of the upper-echelon Democrats are still operating with a majority-party mindset.
A minority party has to be strongly disciplined, so that dissension among its members doesn't further reduce its effective number; it has to allow a few members to control the others, so that it can plan its future course as a unit; it has to be willing to fight over every small detail, so that its agenda doesn't fall down the slippery slope; it has to form strong ties to non-governmental organizations, because it can't compete with purely political resources; it has to
hate the ruling party, to give itself cohesiveness and a common goal; and it has to inspire extremely strong devotion to its cause among its supporters.
When a majority party acts like that, though, it's a disaster. It is unable to compromise with the minority party, and uses its superior numbers to control every political issue. Far too much power is concentrated in the hands of a few members. The party's ties to non-governmental organizations create divided loyalties - recently, for instance, the Republicans' strong ties to lobbying organizations has caused corruption - and leads to these organizations becoming agencies of government, as happened with certain churches and lobbyists' groups.
An effective majority party, on the other hand, is much more divided. If the voters see that it acts as a unit or at the behest of a few powerful people, they'll eventually sour on it, as they are now souring on the Republicans. Members try to differentiate themselves from each other, in order to avoid creating the impression of a monopoly or cabal. The majority party can't be seen to be trying to eliminate the other party, for similar reasons. It doesn't have to struggle as hard for power, so it's not as active with canvassing and so forth.
A lot of the older Democrats got their political training and experience in the age of Democratic majority, so their instincts are best adapted for such a situation. The public criticism of other Democrats, the reluctance to attack their opponents... remember how speakers at the 2004 convention were forbidden to attack Bush? That move would have made a lot of sense for a majority party, but as it was we all thought it was nuts. This is because most of us are either fairly young, or didn't become politically active until recently. We became politically aware during the age of Democratic minority, so our instincts are those of a minority party (although we haven't gone as far as the Republicans went, thank goodness). We are trying to push the Democratic party to adopt tactics that make more sense for its current situation, while still preserving the morals that the Republicans abandoned in their quest for a majority.