How to interpret news that D.C. businessman and political kingmaker Jeff Thompson has been able to keep federal investigators from digging into documents that might expose a trail of corruption all the way to Mayor Vince Gray?

We learned this week that prosecutors have accused Thompson of obstructing their investigation into a “shadow campaign” that raised $650,000 for Gray’s 2010 mayoral campaign. The FBI seized the documents from Thomspon’s home and office last June.