It’s the netroots. Of course.

The Wall Street Journal’s Dan Henninger put his finger on it in this piece analyzing what went wrong for the sure winner of race to be the Democratic presidential nominee. In the framework of film tragedies.

Has anyone else out there begun to find that it is easier to make sense of the struggle between Hillary and Barack if one thinks in terms of film tragedies? Several have been unspooling in my mind these days: “All About Eve,” “Sunset Boulevard,” “A Star Is Born,” even “Bonnie and Clyde,” if one assumes the Clintons are going to either pull off this heist or go down in a blaze of bullets.

Hillary’s star is being eclipsed. Why?

A year ago, Hillary Clinton assumed the effort would bring her the prize. Instead, it has brought her to the precipice. What happened? What was supposed to be triumph has turned to tragedy. Who rewrote the plot?

And here he unravels what perhaps changed the course of history, odd as that may sound.

The first revision came at the hand of Howard Dean. The Vermont governor’s quixotic 2004 presidential run did one big thing: It let the netroots out. It empowered the Democratic Left. Web-based “progressives” proved they could raise lots of political money and bring pressure, especially when allied with labor unions.

They didn’t defeat centrist Joe Lieberman in 2006, but they drove him out of the party. They pushed the party’s Iraq policy under Harry Reid and Nancy Pelosi into total, rejectionist opposition. In this world, the Petraeus surge is a failure, period. Thus, Obama calmly gives the surge little or no credit. Also in this world, trade and Nafta are anathema, as seen in the House refusal to pass the trade agreement with Colombia, the U.S.’s strongest ally in South America.

What the netroots has done is bunch up the party ideologically. While the Republican Party slices conservative ideology as thinly as aged prosciutto, the Democrats, in Congress and on the presidential campaign trail, are all swinging a populist anvil — with the left hand.

Forget moderation and centrism. Swing for the fences.

On trade, the Democratic Party is as far left as at any time in its history. Both Al Gore and John Kerry ran as economic populists, but there was nothing on trade like what we have heard in this campaign.

Those of us in Chicago have been there before. We are the constituents of Barack Obama. We know the Democratic party.

The Democratic platform may be familiar, but it is also infused with the quality of a dream. Actually, the word “dream” gets used a lot in Democratic rhetoric. What are essentially bureaucratic arrangements, such as health insurance or after-school programs, are promised as “universal.” Meanwhile, “the middle class” is being offered a version of never-never land…If you are selling a dream you need the best possible salesman to make it seem somehow possible. They found him in Barack Obama…

The bitter irony is that what the Democrats want is someone like the original Clinton, another figure who can make the old-time religion sound not like a government program, but personally uplifting. She can’t.

We’re about six days away from the last close-up. What Hillary Clinton has invested, given and endured for her party to get to this moment is hard to imagine. Then the Democratic audience says: What difference does that make? A star has been born.

The bitter irony is that what the Democrats want is someone like the original Clinton, another figure who can make the old-time religion sound not like a government program, but personally uplifting. She can’t.

We’re about six days away from the last close-up. What Hillary Clinton has invested, given and endured for her party to get to this moment is hard to imagine. Then the Democratic audience says: What difference does that make? A star has been born.

We saw this in the Illinois elections of 2004. We could have predicted this for the nation this year, given what happened in that election. Obama was not the “machine” candidate. He won anyway. I’m not the least bit surprised, having covered that race.

The bitter irony is that what the Democrats want is someone like the original Clinton, another figure who can make the old-time religion sound not like a government program, but personally uplifting. She can’t.

We’re about six days away from the last close-up. What Hillary Clinton has invested, given and endured for her party to get to this moment is hard to imagine. Then the Democratic audience says: What difference does that make? A star has been born.

What else matters? Maybe it’s time for celestial navigation.