Obama backer pens op-ed to explain endorsement of Obama over Clinton, despite his ties to the family, saying while he “seriously contemplated endorsing Sen. Clinton, I never told anyone, including President Clinton, that I would do so.”

Also denounces Carville’s comments and overall negativity in the race.

“Carville has made it very clear that this is a personal attack — driven by his own sense of what constitutes loyalty. It is this kind of political venom that I anticipated from certain Clinton supporters and I campaigned against in my own run for president.”