4) The obvious unknown: Is the embarrassing information about Mr. Trump true?
CNN reports that, in the time since the former MI6 operative approached the FBI over the summer, ”US intelligence agencies have now checked out [him] and his vast network throughout Europe and find him and his sources to be credible enough" to warrant briefing the president and president-elect on his findings. Many of Tuesday's reports, in other words, depend on the credibility of one anonymous source and what he told the intelligence community. The cautionary tale there is that ”Curveball," an Iraqi defector the U.S. relied on to build its case about WMD in Iraq, was also thought to be credible—until many of his claims proved false. And, as Buzzfeed notes, the full document contains errors of spelling and fact.
The fact that the intelligence officials thought the allegations serious enough to bring to the attention of the president and the president-elect is something we need to give serious weight to. But there's also an unprecedented element in this story, which concerns claims about politicization of intelligence. What intelligence officials don't want to have is for news to leak before the president or president-elect sees it directly—they want Obama and Trump to hear it from them first. Then the problem is, once that's happened and the news leaks anyway, it seems to have more credibility precisely because it was brought to such high-level attention.