As the denizens of Afghanistan prepare to vote in tomorrow's presidential election (presumably defying threats by the Taliban to cut off their noses and ears), I couldn't help but wince at what Richard Holbrooke said the other day. During a Washington forum, President Obama's special envoy to the volatile region summed up the status of the war this way:

"The specific goal of the United States is really hard for me to address in specific terms. But I would say this about defining success in Afghanistan...We'll know it when we see it."

Good grief. How reassuring.

If Obama and his top foreign policy players can't communicate better than that - if they can't specify the goals, spell out the strategies for achieving those goals, and provide Congress with the metrics by which progress toward those goals can be measured - they could take a big political hit on the home front. Not right away, but quite possibly within a year.

And the complaints about the war's purpose, prognosis, and costs (in blood and treasure) would likely come not from the Republicans (who are broadly supportive of our Afghanistan effort), but from Obama's liberal base. This pattern is already taking shape in the public opinion polls.

With respect to war goals, Obama himself has actually been a bit more specific than Holbrooke; back in March, he stated that our aim is to stabilize the country and deny safe havens to the terrorists who yearn to attack us again at home - in his words, we're fighting "to confront a common enemy that threatens the United States, our friends and allies, and the people of Afghanistan and Pakistan who have suffered the most at the hands of violent extremists."

He wants to do this by stepping up our military effort against the Taliban (we're slated to have a record-high 68,000 troops by year's end, with hints that the tally could be upped by another 10,000); by providing greater protection to Afghan civilians; by nurturing a larger and more effective Afghan military force. For starters, of course, the viability of Obama's plans may well hinge on whether tomorrow's elections can produce a government that is viewed by most Afghans as credible and legitimate.

The real problem, with respect to what Obama on Monday called "a war of necessity," is that he hasn't yet come up with criterion by which progress (or lack thereof) can be measured. Obama set the bar for himself back in March when he promised, "We will set clear metrics to measure progress and hold ourselves accountable." The Democratic Congress wants to see these criterion by Sept. 24, which happens to be a congressionally-mandated deadline for a progress report on the war.

And the Obama team says it understands the public's concern; as a top Obama aide told Politico 11 days ago, "Because we believe the American people deserve clarity on our progress in Afghanistan, we have compiled a comprehensive set of metrics based on the objectives laid out by the president and informed by a stringent intelligence review."

Presumably these metrics will be better than the Bush metrics in Iraq. But they'll be tricky nevertheless. How does one accurately measure a drop in government corruption? A more vibrant economy, freed from drug lord largess? Or a rise in the quality of American-trained Afghan army forces? Or the effectiveness of American aid programs? (Regarding the latter, Holbrooke warned the other day that "our civilian assistance is going to continue for a long time.")

Most liberal Democrats thus far have cut Obama a lot of slack, but I have already detected some restiveness within the think tank and academic communities. Michael Cohen, who blogs for the National Security Network, which is heavily populated by Democratic establishment types, warned the other day about "mission creep," and said that "I have become more and more convinced...that the administration has no clear sense of what the end game is in Afghanistan and what they are trying to achieve there. Day by day we are wading more deeply into what looks like a military and political quagmire for which we have no clear plan of success."

Andrew Bacevich, a retired Army colonel who now teaches international relations at Boston University, wrote the other day that he has no problem with the goal of denying al Qaeda safe havens in Afghanistan; however, that goal "shouldn't require military occupation by the United States and its allies." He argued that "intensive surveillance complemented with precision punitive strikes (assuming we can kill the right people) will suffice to disrupt al Qaeda's plans. Certainly, that approach offers a cheaper and more efficient alternative" to a large-scale, long-term military occupation, which "has the unintended effect of handing jihadists a recruiting tool."

Even Lee Hamilton, the former centrist Democratic congressman and intelligence maven, voiced skepticism last week in a newspaper column: "In allied capitals, an important factor is the war's popularity, and therefore sustainability. Public support is beginning to wane as success appears elusive...Many members of Congress, though hardly a majority, already view the war effort with a great deal of skepticism...(I)s this type of war really the best use of American power and resources in today's world?"

Granted, Obama is stuck with trying to straighten out a war effort that his predecessor launched, then ignored (in favor of invading the wrong country), then dumped in Obama's lap. But this doesn't mean that most Americans will be eternally patient about Afghanistan - particularly those Americans who happen to vote Democratic.

July was the bloodiest month for allied forces since it all began in 2001. It's striking that, according to the latest poll conducted by CNN and Opinion Research Corp., three quarters of all Democrats now oppose the war - while nearly two-thirds of Republicans support it. The Democratic deficit could spell trouble for Obama next year. If his war metrics look bad on the eve of the 2010 congressional elections, that could give disillusioned Democratic voters one more reason to stay home. The party with insufficient passion tends to perform badly in off-year elections, as Democrats recall about 1994.

And here's what our top commander in Afghanistan, Gen. Stanley McChrystal, had to say about the war, when interviewed last week by The Wall Street Journal: "It's a very aggressive enemy right now. We've got to stop their momentum, stop their initiative. It's hard work."

It's hard work...There's a guy down in Dallas, by the name of George W. Bush, who used to utter that phrase all the time while pleading for patience in Iraq. Look what it did for him.