Is this good news or bad news? It’s good news, of course, if he can negotiate a better arms-control deal — but if he can’t, and New START dissolves, suddenly we’re staring at a new nuclear arms race with Russia, a prospect Trump has explicitly placed within the realm of possibility in the recent past.

I take it as a good sign that he’s pushing back against Putin in negotiations, whatever the subject. The fact that he might not have known what New START is before Putin brought it up, though, is … less of a good sign:

When Putin raised the possibility of extending the 2010 treaty, known as New START, Trump paused to ask his aides in an aside what the treaty was, these sources said.

Trump then told Putin the treaty was one of several bad deals negotiated by the Obama administration, saying that New START favored Russia. Trump also talked about his own popularity, the sources said…

Typically, before a telephone call with a foreign leader, a president receives a written in-depth briefing paper drafted by National Security Council staff after consultations with the relevant agencies, including the State Department, Pentagon and intelligence agencies, two former senior officials said.

Just before the call, the president also usually receives an oral “pre-briefing” from his national security adviser and top subject-matter aide, they said.

Reuters’s sources claim Trump did not receive the NSC briefing paper before the call. Whether or not he was briefed by Flynn, they were unable to confirm. All of which raises the question of whether his opposition to New START is now fixed or whether it was just something he said in the moment to hide the fact that he hadn’t studied for that day’s test, so to speak, and was operating on the assumption that any deal Obama had agreed to must necessarily be bad. The truth may lie somewhere in between: Even if Trump didn’t know the ins and outs of New START, he might have recognized Putin’s interest in extending it as leverage he can use in broader negotiations with Russia. Remember, he told a British paper a few weeks ago that he might lift sanctions on Russia over Ukraine in return for a “nuclear-arms reduction deal” — which is precisely what New START is. It could be that Trump is eyeing more significant nuclear concessions by Moscow as the price of ending sanctions; if so, he’ll obviously need more from them than what New START currently provides.

Or, here’s another possibility: The entire Reuters story is “fake news” garbage.

Maggie Haberman is a NYT reporter with lots of sources inside the White House, judging by the dishy stories she’s filed over the last few weeks. If she’s telling you that Trump knows New START well enough to have been chatting about it with others recently, there’s good reason to believe it. Which means either (a) the Reuters story is a hit piece fed by anti-Trump sources or (b) the Reuters story is a gross exaggeration of what actually happened. Maybe Trump paused the call with Putin because he needed reminding about a particular detail of the treaty, like the exact number of warheads it allows to each country, but was otherwise conversant in the basics of New START. Either way, if the story’s not credible, how can we trust that Trump wasn’t briefed beforehand according to traditional protocols, as Reuters’s sources claim? Granted, that seems plausible given how oddball some of his diplomatic engagement has been lately, but if Reuters is wrong about how much Trump knows about New START, there’s no reason to believe the other key details. (Although, in fairness to them, the idea of Trump rambling on at Putin about his “popularity” seems only too plausible.)

Whether you believe the Reuters story or not, this is another neon example of highly-positioned leakers within the administration making Trump look amateurish and ill-prepared, a phenomenon that Haberman and various other reporters have dined out on ever since the inauguration. Reuters claims no fewer than three sources for this piece: “Two of the people who described the conversation were briefed by current administration officials who read detailed notes taken during the call. One of the two was shown portions of the notes. A third source was also briefed on the call.” Who’s doing all the leaking? And how long will it before the number of deputies briefed on Trump’s communications with foreign leaders shrinks to a very select few in the interest of preventing leaks, leaving officials across various agencies uncertain of exactly what’s being said by and to the White House vis-a-vis foreign regimes? They need to find the leakers. Exit quotation from a Trump ally: “It seems that everyone [there] has their own leaking apparatus.”