His name was well known in courts and in corporate suites across the metropolitan region and revered in the halls of Trenton. But a single imprudent word, written by a subordinate, brought David Samson more notoriety than he could have ever desired.

“Retaliate.”

The word was forever fastened to Mr. Samson, Gov. Chris Christie’s appointee to head the Port Authority of New York and New Jersey, when a trove of emails was released about the closing of access lanes to the George Washington Bridge in September. The subordinate, David Wildstein, used it to describe how Mr. Samson would deal with a New York appointee at the authority who had reopened the lanes.

“Samson helping us retaliate,” Mr. Wildstein wrote.

The unearthing of that line brought a harsh focus upon Mr. Samson and the intersections between his efforts to advance Mr. Christie’s agenda at the Port Authority and the work of the law firm he co-founded 42 years ago.

After months of news articles exploring those potential conflicts of interest, and a subpoena from federal prosecutors earlier this month, Mr. Samson had tendered his resignation from the Port Authority, Mr. Christie announced at a news conference Friday. “He is 74 years old, and he is tired,” Mr. Christie said.