WHAT: Tom Ross, unpaid chairman of the Delaware Republican Party, received an e-mailed death threat castigating his backing of GOP Rep. Mike Castle over tea party challenger Christine O’Donnell in today’s Senate primary.

WHO: O’Donnell’s campaign denied any connection to the threat, saying Castle would be the beneficiary if the O’Donnell candidacy is seen as inspiring political intolerance or even violence.

WHAT’S BEING DONE: The threat is under investigation and Ross temporarily left his home. Identity of the e-mailer has not been confirmed, but the sender reportedly “wrote his name and address” on the note.