Five candidates, including frontrunner Boris Johnson and Rory Stewart, make it through to the next round.
A judge said their online propaganda for a group called the Sonnenkrieg Division was abhorrent.
The move is a "precautionary step" to protect students, says Edexcel's parent company, Pearson.
Russell Wadge, 57, is charged with five offences relating to explosives and poisons.
The opening day of Royal Ascot proves to be a family occasion for the Queen.