And they saw the Port Authority of New York and New Jersey and its resources — money, jobs, symbolic artifacts from the wreckage of the World Trade Center after the Sept. 11 terrorist attacks — as assets that could be traded for endorsements and support in both campaigns.

“Just to be clear, at some point hundreds of flags flown over the WTC will find their way to VFW’s all through Iowa, New Hampshire and South Carolina,” David Wildstein, a self-described “enforcer” for Mr. Christie at the Port Authority, wrote in September 2012 to Bill Stepien, the governor’s deputy chief of staff, who would go on to run Mr. Christie’s re-election and was expected to run the presidential campaign.

“I was conveying to Mr. Stepien that the flags that could be used to the governor’s political advantage in New Jersey could be used in those three states,” the first three to vote in presidential primaries, Mr. Wildstein said in federal court here Friday.