But that latter commitment will produce future trouble for the President, for at least four reasons.
First, underlying the McChrystal downfall is the fact that there is discord within the administration about Afghan strategy and tactics. Obama's decision last year to send more troops was a compromise between two positions, and those positions remain unreconciled. On one side were Petraeus and other military leaders arguing for considerably more troops than Obama approved. On the other side stood Vice President Joe Biden and liberal congressional Democrats pressing a "drone" strategy that would rely on automated weaponry and a withdrawal of ground troops.
Those positions are still present in the administration, and they have bred distrust and discord over the Afghan policy. As Philadelphia Inquirer columnist Trudy Rubin put it last week:
McChrystal's staff made snide remarks to Rolling Stone about Vice President Biden, Ambassador Richard Holbrooke, and National Security Adviser James Jones. The general complained about being "betrayed" by Karl Eikenberry, the U.S. ambassador to Kabul. Obama argued that the Rolling Stone piece "erodes the trust necessary for the team to work together."
What trust? The article reflects serious tensions between Obama's civilian and military advisers in Kabul, fed by the conflicting positions of White House and cabinet officials on Afghan strategy. These tensions make it impossible to fashion a coherent policy that Americans -- and Afghans -- can understand.
A second reason that future trouble is coming for Obama is that there is no certainty that more administration unity will appear, even with Petraeus in charge.
Third, Obama has now empowered Petraeus, in effect depending on him to deliver victory. It will be difficult for the President to disavow Petraeus in the future, given the general's impressive success in Iraq. That suggests that Obama may have to disappoint liberal Democrats on Afghanistan in the future by keeping troops there longer than his self-imposed deadline in 2011.
Fourth, even with an extended commitment, victory is far from certain. Petraeus indicates Afghanistan is a greater challenge than was Iraq. If so, Obama's future political and military difficulties resulting from Afghanistan are likely considerable, even if more unity appears in our Afghan policy.
So a smart move by Obama last week still leaves him with a host of Afghan difficulties that will bedevil his presidency in the coming months.