This is the shadow that hangs over the NATO summit in Chicago today. The leaders are planning their exit strategy from Afghanistan and trying to sell it as a mix of leaving and staying: The main combat forces will turn over the lead role to the Afghans in mid-2013, and leave in 2014; a smaller counterterrorism force will stay for another 10 years to train the Afghans and chase the bad guys.

President Obama expressed the best-case version of the future in a statement Sunday after he met with Afghan President Hamid Karzai. He talked about a “shared vision that we have in which Afghanistan is able to transition from decades of war to a transformational decade of peace and stability and development.”  

But what about the Taliban? Unfortunately, they have a vote, too. If the past is any guide, they’ll go right to the points of greatest U.S. vulnerability — infiltrating their assassins into the Afghan security forces so that the United States stops trusting its allies, and mounting spectacular large-casualty attacks at U.S. bases and international gathering points, to sow fear and demoralization.

CIA analysts, who have been skeptical for years about the prospects for success in Afghanistan, apparently see the Taliban regaining strength — contrary to the U.S. military’s assessment that the insurgents’ momentum has been checked. That’s what I took from the comments of Sen. Dianne Feinstein and Rep. Mike Rogers, chairs of the Senate and House intelligence committees, respectively, after their visit to Afghanistan this month. “I think we’d both say that what we’ve found is that the Taliban is stronger,” said Feinstein — and she didn’t hear that from Gen. John Allen, the overall U.S. military commander, who is trying to be a good soldier and make the president’s plan work. More likely, the skepticism is a CIA view.

And to ask another meddlesome question, as the Chicago summiteers prepare the upbeat talking points: What about the other ethnic groups and warlords in Afghanistan that have the jitters about NATO’s departure, even as the Taliban is licking  its chops? What will the United States do if the Tajiks draw closer to the Northern Alliance militia in northeastern Afghanistan or the Hazaras deepen their alliance with Iran, which is proving a potent force in western Afghanistan?

These other ethnic groups (along with non-Taliban Pashtuns) are as important to the future of Afghanistan as the Taliban leadership hiding out in its Pakistani sanctuaries. So I hope the United States will spend a little more time working on the political transition in Afghanistan, even as it plans for the military transition. The goal should be to form a political alliance for a sane, non-terrorist Afghanistan that can extend beyond the shelf life of the Karzai government, which expires in 2014 (or maybe even earlier, with speeded-up elections).

If there’s one thing that Afghanistan proves, it’s that warlike people abhor a vacuum: If power is up for grabs as NATO forces begin leaving, another shootout will begin. What will the U.S. answer be?

Well, officially (and in fact), we are betting that the Afghan security forces will be strong and cohesive enough to hold Kabul, maybe Kandahar and the ring road that links the country — providing a ragged version of “Afghan Good Enough” for the future. Tajiks and Hazaras will probably be free to have their militias under this scenario, so long as they keep the roads open and feed timely intelligence about al-Qaeda or Taliban terrorism to U.S. counterterrorism operatives.

But what if the center doesn’t hold? What if the Afghan forces collapse under fire and key Afghan government facilities are overrun? I frankly doubt the United States would send major forces back to prop up the government. Which means, I guess, that Plan B is civil war and an eventual partition.

Oh yes, about that bet: My friend the veteran diplomat predicted that two years after the 2014 withdrawal of most NATO forces, the Taliban will be back in control in Kabul.

Updated: 10:55 a.m., May 21, 2012