We still don’t know if Mueller has evidence linking a Trump associate to the Russian effort. But if he had solid evidence that an American aided the Russians, that could be a very difficult case to defend against. Jurors would have little patience for technical legal arguments as long as Mueller had proof that the American knew what Moscow was doing.
It also could have profound implications on another aspect of defense strategy in this case. There has been much speculation that Trump could pardon associates who were charged with committing crimes. For example, one could imagine the president pardoning someone who made a false disclosure or engaged in tax evasion.
But pardoning someone who worked with the Russians to undermine our election would carry a steep political cost. If legal counsel for Trump associates come to the same conclusion, and believe a pardon is not forthcoming, that could make their clients more willing to cooperate with the Mueller probe. The most important factor that people consider when deciding to flip is the likelihood that they will serve significant prison time.