"That notion came to me in Paris in 1983 when I was teaching at the St.-Denis (formerly Vincennes) campus of the university. I was trying to explain American politics to my students when I suddenly realized that I could simplify their lives and mine by telling them that there were no political parties in the United States. The Democrats and Republicans, I said, were not parties in any European sense of the word. They were undisciplined and periodic coalitions, which came together on the basis of electoral opportunism every two years -- and in a national sense, only every four years. They had no real program, and the platforms adopted by party conventions were, by the common consent of all, simply consigned to the wastebasket once they were voted.
"The institution of the primary, I continued, was a marvelous, and uniquely American, example of this organized anarchism. In Europe, the parties of the Left tend to name leaders on the basis of a political viewpoint and, in any case, only dues-paying members of the party have the right to elect delegates, who in turn select that leader. Even conservative parties such as the British Tories have some kind of a mechanism whereby leaders 'emerge.' Moreover, in the parliamentary system it is quite common for victorious parties to enact their entire electoral program. That happened in the 1945 Labour government in Britain and as a result of the Socialist triumph in France in 1981-1982. But in the United States anyone who declares himself or herself a member of a party can, without the payment of dues or the affirmation of a single political principle, help determine the leadership, program, and policies of the party.
"Indeed, it was only in my own lifetime that the custom of crossover voting in primaries was eliminated. That is, it used to be quite easy for voters to select the party to which they 'belonged' on primary day itself. This meant that Democrats could vote in the Republican primary to select the worst possible candidate from the Republican point of view, and that Republicans could return the favor. Under such circumstances, I told my students, it was all but impossible to have a serious, disciplined party -- indeed to have a party in any sense of the word -- since elected officials responded to their amorphous, unorganized base and not to any institution.
"This puzzling fact was one of the reasons why generations of American socialists had committed political suicide. They had attempted to create a party and movment in the United States on the European model -- only that model didn't apply. It took a long time for American socialists -- and for me -- to grasp this home truth. We righteously pointed out that the Democratic party contained a good number of the most reactionary people in the United States: not just crooks and swindlers, which was obvious enough, but union busters, militarists, racists, sexists, and just about every single variety of political desirable. What we did not notice was that, *at the very same time*, the Democratic party had, since the New Deal, also contained the clear majority of the progressive forces. That was, and is, a blatant contradiction. A very American contradiction."
(Michael Harrington, THE LONG-DISTANCE RUNNER, 1988, pp. 67-68.)
Louis Proyect (http://www.panix.com/~lnp3/marxism.html)