Assassination in Najaf

Unfortunately on deadline today and unable to give a full accounting or analysis on a news-heavy day. Daily Kos has an item on the attack.
Initial response based on NPR: This is very, very bad (obviously). Twenty 75 More than 90 people dead and at least 140 wounded. The most holy shrine to Shi’a Islam is damaged [UPDATE but not too badly, apparently.] Ayatollah Mohammad Baqir al-Hakim, a key Shi’a cleric and head of the SCIRI, is dead. Shi’ites in Najaf seem to be blaming remnants of Saddam’s security forces for the attack. (Which seems plausible.)
Hakim’s death could shatter the Iraqi Governing Council, on which Hakim’s brother, Abdul Aziz al-Hakim, sits. It could set off a power struggle among the Shi’ites with the moderates — now possibly led by Abdul Aziz al-Hakim (who isn’t even that moderate, frankly) — and the hard-liners, led by firebrand 22-year-old Moqtada Sadr.
If it turns out that Sunnis were behind this, expect riots and clashes in Baghdad.
Iran will be watching this very closely as well. Hakim was their guy in Iraq and it’s unclear now what will happen.
Tin-foil hat theory of my own: Al Qa’ida operatives, who are Sunni, did this in a bid to spark a civil war, which would embroil U.S. troops and tie them down when they might be needed in South Korea, Indonesia, Afghanistan, etc. The attack also aims to show the Arab world that American troops aren’t up to providing security and can be put on the defensive. This will embolden _jihadis_ and give other nations yet another reason to withhold additional troops. All this means America will likely remain pretty much on its own in Iraq and her ability to respond to threats around the world will be negatively impacted. Instead of flypaper for terrorists, Iraq is a tarbaby for America.
This could be the equivalent of the assassination of the Archuduke Franz Ferdinand that sparked World War I — although on national scale, rather than a global one. The probability of civil war — with American troops caught in the middle — just spiked.