The AP reports:

The Obama campaign offered no details to support the captain's story, making it impossible to verify. A spokesman did not immediately respond to questions about who the captain was and when and how the candidate learned about the allegation.

ABC News said it talked to the unidentified captain, whose account of shortages in Afghanistan was for the most part accurately summarized by Obama, although not verified.

The captain said, however, that the unit did not go after the Taliban for the purpose of getting their weapons, but sometimes used those weapons when some were captured.

"For the most part" is a generous description. Aside from Tapper's faith in the captain as credible, the story remains unverified, and, in fact, "impossible to verify," since the Obama campaign has not released any detail that might corroborate the account. Even if one takes the captain's story at face value, there is a large discrepancy between the story he tells and the story Obama told in last night's debate (mainly that there was no ammunition shortage, and that the unit was equipped with a full compliment of weapons).

But at this point the captain's story cannot be taken at face value, and confirmation of his account cannot be left solely to Jake Tapper's assessment of the captain's credibility. Confirmation requires something beyond the word of an unnamed captain who found his way to a meeting with Barack Obama's staff at some unspecified date in the past. Obama has leveled a specific and unsubstantiated allegation that remains, by any objective analysis, "impossible to verify."