According to interviews and court documents discovered by The Washington Post on Wednesday, a Washington DC businessman allegedly spent more than half a million dollars on canvassing efforts for Hillary Clinton in 2008, and that same man is now under investigation for failing to disclose such efforts to the Federal Elections Commission.

[Jeffrey E.] Thompson allegedly paid Troy White, a New York marketing executive, more than $608,000 to hire “street teams” to distribute posters, stickers and yard signs beginning in February 2008 to help raise Clinton’s profile during her primary battle with then-Sen. Barack Obama, according to the documents and interviews with several people familiar with the investigation.

When White pleaded guilty on tax charges earlier this week, the documents also revealed his efforts for the Clinton campaign in at least four states in 2008. Senior officials who worked on Clinton's campaign that year told the Post that they either had no knowledge of White's actions or had never even heard of him.

Thompson has not yet been charged with any crimes, specifically regarding his involvement in the 2010 mayoral candidacy of Vincent Gray. The investigation into Gray, which subsequently led to White, has now reached Clinton, the most prominent person who is potentially implicated.

Clinton's involvement likely seems incidental, however:

Court documents and interviews indicate that in early 2008, as Clinton struggled to make up ground against Obama in the primaries, White directly approached the Clinton campaign, pitching his ability to help organize supporters in urban areas. After campaign officials declined his services, a longtime Clinton adviser, Minyon Moore, helped connect White with Thompson, who agreed to fund his canvassing operation, according to the documents and interviews.

Clinton's campaign was not on the hook to report this activity, since individual entities are supposed to report their own financial operations run in support of a candidate. The flip side of this, however is that they are prohibited from coordinating their efforts with a campaign directly. Documents detailing conversations between White, Moore, and other campaign officials may constitute a coordinated effort.

A Clinton spokesperson released a statement, saying, "As the court document filed in this matter clearly states, the Committee turned down Mr. White's services. The Committee will not have any further comment in an ongoing investigation."