“President Trump last week signaled to the world that the United States would prematurely withdraw from Syria,” McCain said. “Bashar Assad and his Russian and Iranian backers have heard him, and emboldened by American inaction, Assad has reportedly launched another chemical attack against innocent men, women and children, this time in Douma.”
The comments came on an otherwise pretty politics-free weekend, but the severity of what McCain said shouldn't escape anyone's notice.
McCain did choose his words carefully so as not to completely lay what happened at Trump's feet. He doesn't directly tie Trump's withdrawal comments to the chemical weapons attack. But he does seem to lump them in with “American inaction,” and the clear implication is that the Assad regime has decided to act in a way it might not otherwise have acted — were it not for Trump signaling that the United States would soon be gone and doesn't really want to be there.
Whether that's what actually happened is an open question. It also seems entirely possible that the chemical weapons attack could prolong the U.S. presence in Syria in a way that wasn't really in the plans. If Assad is looking forward to the United States being gone, this would seem to be a somewhat odd course of action.
But just take a step back for a moment and think about how serious a charge this is. Trump earned criticism on the campaign trail for suggesting that George W. Bush was indirectly to blame for the attacks on Sept. 11, 2001. (“The World Trade Center came down during the reign of George Bush. He kept us safe? That is not safe.”) What McCain's saying here isn't that far afield of that charge.
Update: White House press secretary Sarah Huckabee Sanders responded to McCain's comments Monday afternoon. "I think that it is outrageous to say that the president of the United States green-lit something as atrocious as the actions that have taken place the last several days."
McCain, notably, did not say Trump "green-lit" the attacks -- only that his policies emboldened Assad to carry them out. "Green-lit" implies explicit permission.