I'm not sure how the politics or timing benefit Barack Obama, in this instance. When you're trying to get a new Russia/US arms treaty through Congress, I'm not reminding the American public that the Russians are our enemy, and they are actively engaged in espionage in our country, furthers that goal.
Moreover, it's clear that this spy ring was compromised years ago, during the tenure of the previous president. It's tough to paint the previous administration as disinterested and feckless when they are the ones who clearly deserve credit for this lengthy counter-intelligence operation.
On balance, this story does much more to undermine Obama, than it does to help him.
...When you're trying to get a new Russia/US arms treaty through Congress, I'm not sure reminding the American public that the Russians are our enemy...