"Grynt!"

Mr. Romney does have his own distinctly G-rated arsenal of angry expressions -. "Good grief", "flippin'", "good heavens", and even the occasional "crap".
  Perhaps the most intriguing of these is "grunt". Most people just grunt. Mr. Romney, however, talks about grunting. "Grunt" he says, onomatopoetically, when annoyed with a last-minute change in his campaign schedule,

- New York Times i dag, overskrift: "Gosh, Who Talks Like That Now? Romney Does"