Second, when the GOP moved to the right under Reagan, it succeeded because it moved closer to where the country was, hence the "Reagan Democrat" phenomenon. No similar "Dean [or whoever consummates the revolution] Republican" movement can be expected; that is, moving the Democrats to the left will not do the same, because that's not where the country is. America exists in the middle: a bit to the left of Bush (though not as much as it thinks), but well to the right of someone like Gephardt. The fact that Dean's selling point is that he's from the "Democratic wing" of the party (and presumably Gephardt is not) will not win him the center.
The third important point was that Goldwater and Reagan were both WYSIWYG politicians; in other words, their heart-on-the-sleeve ideology was their selling point to the electorate -- in Reagan's case a successful one. (And, again, it worked because that's where the country was.) Dean seems like a cipher. What is his ideology? No war in Iraq? Why, then, does he push intervention in Liberia, when clearly America's interests lie more in Iraq? (Update: Here we go! Someone ask Dean why this isn't a distraction from the war on terror.) Civil unions? Like Green, I welcome the idea, but it's not like Dean sweated for it; the Vermont judiciary brought it about. What else is he for? Reducing the deficit? A great thing to be for, until you tell people you'll fix it by taxing the bejesus out of them. Visit the careers of Mondale and Dukakis to see the effect of running on taxes vs. deficit. The public will abide a deficit every time.
In short, I find myself agreeing with Green on many points, but I disagree with his conclusion. Dean is bad for the Dems. He's McGovern, not Goldwater. If you want to see where America is, watch Hillary, who will run in 2008 as a moderate. She's supporting the war in Iraq, hasn't been a carper about WMD (do you really think Bill was allowed to speak on the issue without her say so?), and keeps herself fairly clearly apart, publically, from Tom Daschle -- thus avoiding the whirlpool surrounding him as he slips into irrelevance. The Goldwater (and Reagan, for that matter) of the Democrats was Clinton -- the New Democrat. Why do you suppose the paradigm in liberal politics, on both sides of the Atlantic, is the aptly named Third Way? The second way, traditional Labour (in which direction Dean would take the Dems), is ideologically discredited.