According to Maggie Haberman:

Nelson said the lists were put together after a discussion involving the congressman's chief of staff in his Washington office, Chris McCannell, and done after a conference call with him, the campaign finance team and others.

If true, this could be more bad news for the McMahon campaign. The lines between official government work and campaign work are pretty thick, and electeds will go to great, sometimes absurd lengths to not cross them.

More from Maggie:

  [Nelson] said the impetus for creating the lists came "from the official office...I know [McCannell] was on the phone call. The decision to create that list came as a result of a discussion with the finance (team). He was aware of it."

Asked for comment, McMahon's campaign manager Jonathan Yedin referred to what he told Politico:

Ms. Nelson's actions and statements were unauthorized, inappropriate and not reflective of the congressman or his staff. Congressman McMahon apologized for her behavior and took decisive action to terminate her employment with the campaign. However, this election isn't about Jen Nelson, it's about how best to create jobs, grow our economy, and represent the people of Staten Island and Brooklyn. Mike McMahon has been staunchly independent, working with Democrats and Republicans alike to deliver real results. That's why he will be re-elected in November."

UPDATE: A source close to McMahon just called to clarify that any work McCannell did for the campaign was during his own time, and not part of his duties in the office, a common practice for aides to politicians. My bad.