Watching Gen. David Petraeus testify before Congress inspired several thoughts.

The first is that he has taken on one of the most difficult missions ever given a U.S. commander: building a nation in a region of the Middle East already involved in an incipient ethno-sectarian war.

Petraeus unambiguously identified this as the core struggle we face. "The fundamental source of the conflict in Iraq is competition among ethnic and sectarian communities for power and resources," he said. "The question is whether the competition takes place more -- or less -- violently."

The second thought is that it would be difficult to find a man better suited to this monumental challenge. Petraeus is very smart, honest and tough.

The third is that the courageous troops Petraeus leads are performing as well as military forces can be expected to perform in such a situation.

At one point, Petraeus gave an example of the problems they face. Shiite warlord Muqtada al-Sadr has decreed that his Mahdi Army should take a six-month hiatus from fighting. Some have apparently obeyed his decree -- others have not. As consequence, Petraeus has decided to treat some Mahdi Army members as enemies, some as potential friends.

"We are not going to kill our way out of all these problems in Iraq," he explained. "You're not going to kill or capture all of the Sadr militia any more than we are going to kill or capture all the insurgents in Iraq. And, in fact, what we have tried very hard to do is to identify who the irreconcilables are, if you will, on either end of the spectrum, Sunni and Shia, and then to figure out where do the reconcilables begin and try to reach out to the reconcilables."

"Some of that will have to be done with members of the Jaish al-Mahdi, with Sadr's militia," he concluded. "The question is: Who are the irreconcilables?"

To put this in perspective, recall that we went into Iraq because all of our intelligence agencies with all of their resources could not accurately determine whether Saddam Hussein had weapons of mass destruction. Now, to get out of Iraq, our soldiers must accurately determine which members of a heretofore murderous, Iranian-armed, Shiite fundamentalist militia can be trusted to make peace and which ones cannot.

Yet, in the face of such challenges, our troops have achieved measurable success. "The military objectives of the surge are, in large measure, being met," Petraeus said.

Notably, his assertion that overall attacks in Iraq have been declining in recent weeks was actually corroborated by the contrarian report published on Sept. 5 by the Government Accountability Office. A graph in that report, titled "Average Number of Daily, Enemy-Initiated Attacks Against the Coalition, Iraqi Security Forces and Civilians (May 2003-July 2007)," shows overall attacks peaking in June then steeply dropping.

The very real success of Petraeus and his troops, however, represents only half the surge strategy -- the half our military can accomplish. The other half is political, and must be accomplished by Iraqi politicians.

Petraeus explained this in April. "The focus of Multinational Force Iraq is, of course, on working with our local Iraqi counterparts to help improve security for the people of Iraq in order to give Iraqi leaders the time and space they need to come to grips with the tough political issues that must be resolved," he said.

So far, this half of the surge has failed miserably. None of the major reforms believed necessary to reconcile Sunnis and Shiites have been enacted. De-Baathification has not passed. Oil laws have not passed. Amnesty has not been approved. Provincial elections have not been set. Constitutional amendments have not been adopted.

What did Iraq's politicians do while our troops courageously surged? They indulged in serial boycotts.

After Shiites and Kurds voted in June to remove Iraq's maniacal Sunni parliament speaker (who had accused U.S. forces of butchery and attributed sectarian violence in Iraq to the Israeli Mossad), the main Sunni faction declared it was boycotting the legislature until the maniacal speaker was restored. Shortly after that, Sadr's Shiite faction announced it was boycotting the parliament to protest the new bombing of the Golden Mosque. No sooner had the maniacal speaker been restored, and all factions had returned to parliament, than the parliament adjourned for a month-long vacation.

In August, the main Sunni faction announced it was boycotting the cabinet. Then, the faction headed by former interim Prime Minister Ayad Allawi announced four of its five ministers would boycott, too. But they were merely catching up with Sadr's faction, five of whose members resigned from the cabinet in April.

This leads to a final thought: If Iraqi politicians don't learn how to work their own democracy soon, they may get a bitter lesson in how American democracy works next November. Unfortunately, if significant further progress is not made in Iraq, it will be difficult to avert a U.S. election that brings to power a government committed to a rapid withdrawal from that country regardless of the consequences for the people there -- or for our own national security.