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.