Strange occurrence in US South Carolina Democratic primary.

The only explanation, Mr. Rawl’s representatives told the committee, was faulty voting machines — not chance, name order on the ballot, or Republicans crossing over to vote for the weaker Democrat. With testimony dominated by talk of standard variances, preference theories and voting machine software, the hearing took on the spirit of a political science seminar.

The Washington Post profiled Alvin Greene last week

10 minute video interview with Greene

What happened here?

Wikipedia has a list of possible explanations.

Fivethirtyeight lists possible explanations and analysis.

Rawl and co presented five hours of testimony that the results could only be attributed to a problem with the voting machines.

What is your probability estimate for Alvin Greene's win in this election being legitimate (Greene getting lucky as a result of aggregate voter intent+indifference+confusion, as opposed to voting machine malfunction or some sort of active conspiracy)? What evidence do you need in order to update your estimate?