If Trump does talk to Mueller, there’s a possibility that he could invoke executive privilege to try to avoid answering some of the special counsel’s questions.1 That would be the first formal invocation of executive privilege in the investigation into Russian interference in the 2016 election, although legal experts say Trump is already expanding the power by instructing or allowing aides to refuse to answer questions in congressional testimony in case he wants to claim it later. The power of executive privilege isn’t unlimited. But because the courts and Congress have never established firm boundaries around it, any invocation of executive privilege in this context, whether formal or informal, could lead to a legal showdown in the courts if Congress or Mueller decided to challenge him — and it could also have serious political ramifications.