“Met Romney last week. Tough O Chicago pros will be hard to beat unless he drops old friends from team and hires some real pros. Doubtful,” he wrote.

He added: “US election is referendum on Obama, all else pretty minor.”

This is just the latest in a series of anti-Romney tweets. Last week, the News Corp CEO wrote that Romney “Seems to play everything safe, make no news except burn off Hispanics.”

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