Will foreign policy or principle be Obama's material weakness?

I'm not sure, but I know that unless he improves on foreign policy, then he will not even approach the skill level of President Bush:

Yet the reason Iraq is finally getting that kind of government is precisely because of the surge, which neutralized al Qaeda and gave Prime Minister Nouri al-Maliki the running room to confront Moqtada al-Sadr's Shiite Mahdi Army. And the reason the U.S. can now contemplate more troop withdrawals is because the surge has created the conditions that mean the U.S. would not be leaving a security vacuum. On Wednesday, Mr. Maliki's government assumed security responsibility in yet another province, meaning a majority of provinces are now under full Iraqi control.

Mr. Obama acknowledges none of this. Instead, his rigid timetable for withdrawal offers Iraq's various groups every reason to seek their security in local militias such as the Mahdi Army or even al Qaeda, thereby risking a return to the desperate situation it confronted in late 2006.

The Washington Post has criticized this as obstinate, and Democratic foreign policy analyst Michael O'Hanlon of the Brookings Institution reacted this way: "To say you're going to get out on a certain schedule – regardless of what the Iraqis do, regardless of what our enemies do, regardless of what is happening on the ground – is the height of absurdity."

Mr. Obama does promise to "consult with commanders on the ground and the Iraqi government" in implementing his plans. But he would have shown more sincerity on this score had he postponed Tuesday's address until after he visited Iraq and had a chance to speak with those generals and Iraqis. The timing of his speech made it appear not that he is open to what General David Petraeus tells him, but that he wants to limit the General's military options.

Mr. Bush has often been criticized for refusing to admit his Iraq mistakes, but he proved that wrong in ordering the surge that reversed his policy and is finally winning the war. The next President will now take office with the U.S. in a far better security position than 18 months ago. Mr. Obama could help his own claim to be Commander in Chief, and ease doubts about his judgment, if he admits that Mr. Bush was right.

On the other hand, David Paul Kuhn believes:

Mr. Obama's position shifts are clumsy and ill-timed. He has built his franchise on the concept that he is a new kind of politician. But of late, he has become the reincarnation of Clintonian triangulation.

That does not mean his repositioning is wholly foolish. The timing is foolish. At some point the most liberal Democratic nominee since at least 1984 had to consider the center. Too bad for Mr. Obama that he waited until it appeared politically expedient.

Mr. Obama's moves may test his base as much as the candidate himself. Recall Hubert Humphrey, a pioneer on civil rights in 1948. Two decades later, Humphrey would not repudiate Lyndon Johnson. Humphrey's past liberal stances were forgotten. To some liberals he was on the wrong side of Vietnam, so many in the antiwar base called him no liberal at all. Today's antiwar Democratic base will have to decide how much slack it can offer Mr. Obama when he returns from Iraq.