"Why the US doesn't have a strong Left or social-democratic tradition?"
The long answer is very long; the short answer is "because of racism."
Joanna --------------- Well, here's the intermediate answer, in rough outline:
Because to have Social Democracy, a country must first organize itself something recognizable as Society. That has been historically true until now. But what we have here in the United States is a gigantic market scam disguised as a "society". It has been that way, more or less, since the collapse of the white agrarian settler-farmer democracy at the end of the 19th century. That was a real society, however much we might detest its legacy today, and it was the real foundation of the state and its now hopelessly antiquated Constitution (as Pocock well understood, but Negri did not).
There have been exceptions to The Greatest And Longest Running Scam In World History. The African-American community was one, but it was limited to being a community of oppression, and post Civil Rights, has been largely absorbed into The Scam, oftentimes as the most savvy of Scammers - and nevertheless still victimized as such! The immigrant communities were mistaken - and are still mistaken - for a "sub-society", and have therefore historically been points of attraction for left activism. But almost by definition, immigrant communities cannot comprise the hegemonic social order of a given country. And in a world still divided between nation-states (as against Negri, again - Woods has this right, but ironically for her own argument in Empire of Capital, this supports Lenin's theory), this limitation on immigrant communities places significant limitations on any left strategy based (because as cohesive 'subsocieties', there is something to be 'based' upon, at least temporarily) on them.
As for Doug's question, of course the Democrats provide better _conditions_ for left activism. Under present conditions it would be silly to imagine otherwise. I'd go even further and say that we especially want to see today's Democrat with the Presidency in a period of accentuated crisis such as the one we are in right now. Has it been noticed that, ever since "Pericles'" coup against Carter at the end of the 1970's, the Dems have only been "let into" the Oval Office when it appeared "safe", as it was deemed after the "collapse of communism" and Gulf War. That was a chimera, of course, and the Repubs were ushered back in by hook or by crook in 2000. But while on the "outs", the Dems not only assist in selling and implementing the reactionary Reagan-Thatcher agenda - still in effect to this day - thereby actively _worsening_ the conditions for left activism during these periods, but also help by arranging to nominate "designated loser" candidates for President. And I get the sneaking suspicion that that is the intent behind Kerry, as it was with Gore (and Mondale and Dukakis in the 1980's).
This arrangement, in effect since Carter, reflects the profound political weakness of this ruling class party: especially now, as The Grand Ponzi Scheme Formerly Known As The United States nears, inevitably, its unsustainable vertical hyperbolic asymptote, the former Party of the New Deal does not have a clue as to how to address the situation, other than to Stay The Course. Today's Democrats are designed to ride The Bubble, to blow and be blown in the Oval Office - not to resolve them.
So, in lieu of anything better on the horizon, it would be great if the Democrats won the Presidency - right now! For, unlike in FDR's times, they will not be able to address the economic problems of the United States - yes, even society-less scams have economic problems - in any fundamental way, and at the same time, they will not be able to act in the political-military sphere with the decisiveness of the Bush Gang. No feel good economy, no frenetic flag waving to get in the way.
But - in the manner of Buffalo Chip: LOGICAL FALLACY ALERT! It does not follow _at all_ that "therefore" the Left must actively (or passively!) support Democrats. Not to mention that it will make no practical statistical difference to the outcome, anyway - funny how the hopelessly handwringing Left suddenly gets a swell head about its power when it works in _support_ of the Democrats. A _condition of action_ is not a _course of action_. A course of action is a strategy, the conditions for actions determine the tactics to achieve that strategy. Conditions determine how the course twists and turns, but the strategy always winds up at the same place - unless one has a different strategy in mind.
Last I heard, the minimal strategy was to develop a left politics organizationally and ideologically independent of the ruling class parties. Note there is nothing said here about a "mass base". There is none, as there is no society (from where do you think Thatcher drew her ideological inspiration?). The point of an independent, let's say "anti-Scam" (anticapitalist) politics is to bring that base _into existence_, not only as a political base, but beyond, as the possible nucleus of a Real Future Society once The Scam has been overthrown. To even begin to do that, a political organization must exist independently of The Scam. (In an aside, yes, I know Marx said capitalism is not a scam, and he is right, but this being the epoch of capitalist decay - another valid Lenin idea in his pamphlet that almost everybody has forgotten, although it is so palpably true - not only is there much, much more "decay" to go around than in Marx's time, but the remaining "valid capitalist" processes tend to be disproportionately distributed to places like China, while the growing "decay" processes are just as disproportionately concentrated in places like the United States. And "scam" here refers to capitalism as a "total social" system ("real subsumption", etc.), not just, or not even at all, to the workings of the capitalist law of value. And it specifically references a particular state: The United Scams of America) But that remains the strategy no matter what the conditions, Democrat or Republican, until someone comes up with a better strategy.
That the US Left constantly falls into confusion over the ABCs of politics is simply a measure of how much a part of the general Debauch of America it is.
-Brad Mayer