It's more than a little grotesque to say, but the fact that Iraq has just released Shia Mosque Bombing II: This Time It's Personal has no small amount of relevance to the Presidential election.
Sen. McCain, and to a smaller extent Sen. Clinton, have both publicly boosted the Surge and said that its obvious success show that opponents of the war need to temper their criticism now that the US has turned things around. Except that, of course, it hasn't. What we saw were a number of interrelated events that happened at the same time -- some of them were even deliberately engineered by the US, to their credit -- but none of them were sustainable:
1) The surge itself. Saw a massive increase of US forces in Baghdad, but also at the expense of numbers throughout the rest of Iraq. In any case, can't be maintained for much longer, which is why it was called "the surge."
2) The "Sunni Awakening", which saw the US bribe hostile Sunni tribes to stop shooting at US forces. This worked surprisingly well, but at the cost of arming the most likely opponents to the Shia-dominated Iraqi government, America's nominal ally. (See Matthew Yglesias on this point.) The (temporary?) pacification of Sunni Arabs mitigated the effects of large numbers of US troops moving to Baghdad.
3) The Sadrist ceasefire, since August of 2007, was only ever supposed to last 6 months anyway. Time's almost up.
So, over the next 7 months, what can we expect to see? The key to remember is that, while there's talk about extending the surge by a few months, those US troops are coming home, and soon, in large numbers. The plan is for troop levels to go back to pre-surge levels by July. That leaves... August, September, and October for violence to reassert itself, assuming for some reason that the Iraqis actually wait for the Americans to leave, first. And there's no reason to believe that has to happen.
What would it take for us to see chaos in 2008 like we did in 2006, but (mostly) tamped down in 2007? Well, more of the same, really. Some crisis outside of Baghdad -- and there's no shortage of potential hotspots -- pulls a number of troops out of that city. With lower US troop densities, the Sadrists decide to take on their rivals in the Iraqi security forces. Or maybe the status of the referendum in Mosul will lead to fighting there. But my bet's on the reappearance of Sunni-Shia violence, in a big way. Probably outside of Baghdad itself, for now.
My point -- and I do have one! -- is that for a number of reasons, not all of them within the control of the US government, things in 2008 could get much worse in Iraq. All of the factors which were causing violence in 2006 still exist in 2008. So yes, Iraq will very much be an issue in the election.
So who do you want to be the Democratic frontrunner if, despite the hallowed surge, shit hits the fan? The person who, like McCain, praised the war, the surge, and will be unable to successfully mount a criticism of the same without being accused of flip-flopping? Or a persistent critic of the war who hasn't engaged in the same level of surge-cheerleading?