The event Thursday will raise money for the Republican Governor's Association and Romney is expected to deliver remarks at an evening dinner, according to the Post.
The appearance signals that Romney stands by an embattled Christie, whose administration faces investigations into its involvement in closing lanes on the George Washington Bridge. Romney told CNN in January that he believed Christie was telling the truth when he said he was unaware of his aides' involvement in ordering the lane closures.
"Oh, I sure do. Chris is a friend of mine," Romney said at the time. Chris is a straightforward guy. When he tells you something, you can count on it."