Eric Lichtblau for the NYT:

Interviews with more than a dozen associates, as well as an examination of legal filings, portray Mr. McGahn, 48, as an advocate with an impressive command of arcane election law, but also a fiercely competitive and even intimidating man eager to scrap with opponents — to “duke it out,” as he once said — in pressing the argument that donations of political money are a form of free speech. His Democratic opponents, however, portray him as a master of finding legal technicalities to allow election abuses to go unpunished.

If his record is any guide, Mr. McGahn (pronounced Mc-GANN) will be a fierce proponent of the president’s executive authority to operate independently on a wide range of issues. One key question, however, is how strongly he will push back if Mr. Trump, a man who has defied many norms, seeks to cross into murky legal terrain, a number of associates said.

He may be called on to defend Mr. Trump’s stances on issues like his business empire, his children’s role in his administration, his moves to roll back President Obama’s executive orders, his vow to bring back waterboarding or his threat to impose tariffs on companies moving abroad.