“I had no knowledge or involvement in this issue, in its planning or its execution,” Mr. Christie said. “And I am stunned by the abject stupidity that was shown here. Regardless of what the facts ultimately uncover, this was handled in a callous and indifferent way.”

Mr. Christie’s apology seemed aimed at trying to preserve his carefully developed everyman image. His office sent out video clips of his saddest moments at the news conference. And he offered that he thought voters would forgive him, because they recognize that people sometimes make mistakes and get hurt by even close friends.

Democrats argued that the increasing number of resignations and dismissals — two other aides resigned in December — and the names of the governor’s staff members on the emails made it hard to believe that the pettiness was, as the governor argued, “the exception and not the rule” of his administration.

“I find it hard to believe that Bridget Kelly on her own came up with the idea to divert traffic lanes in Fort Lee,” said Assemblyman John S. Wisniewski, a Democrat who has been leading the investigation.

“You have an administration that is very hands-on,” Mr. Wisniewski said. “It strains credibility to say that somebody in as high a position as a deputy chief of staff, somebody in as high a position as the governor’s principal spokesperson, somebody in as high a position as his campaign manager, all of whose names are in these emails, didn’t ever communicate this to the governor.”

In the questions from reporters, Mr. Christie struggled to explain how his organization could be as close as family — they celebrated birthdays and had parties together — but would not include him in either the decision to close the lanes in September or tell him about it during the months of questions since then.