Barack Obama’s campaign on Tuesday accused Hillary Clinton of planning to “subvert the will of the voters” following reports that she would be prepared to lobby elected delegates to change their vote if the battle for the nomination went to the Democratic convention in August.

The dispute originated from a report on Politico.com, the Washington news website, in which a senior Clinton official was quoted as saying that the August convention would be a “free for all” in which both camps would attempt to poach the other’s pledged delegates.