Bob Kerrey, a former Democratic senator from Nebraska, was a member of the 9/11 Commission.
On the report itself, he once told the press that "There are ample reasons to suspect that there may be some alternative to what we outlined in our version,” and this has been seized upon by some. Here's the quote referenced by NC 911 Truth, for instance:
What is generally missing from these retellings, though, is any scope of exactly what Kerrey believes may be open to question. Which is odd, because it's in the original article. Here's the full paragraph.
"Dismissive of the conspiracy theories", "no evidence" for controlled demolition, "100 percent certain that [bin Laden] directed that attack", and "pretty close to 100 percent certain" about the other issues he raises? Sure, there are doubts here, but they're a very long way away from supporting any significant 9/11 truth talking point, which presumably is why the context of Kerrey's remarks must be removed: they really don't want you to know what he actually thinks.