WaPo helpfully points out that perjury trap, a term thrown around by Trump advisors and lawyers in reaction to reports that Special Counsel Mueller is interested in interviewing President Trump concerning his campaign possibly colluding with Russia during the 2016 Presidential Campaign, is actually a term of art, and not applicable to the interview:
But “perjury trap” is a specific legal defense, related to entrapment. A claim of a perjury trap is really a claim of prosecutorial misconduct. It refers to an abuse of the legal process, whereby a prosecutor subpoenas a witness to testify not for a legitimate investigative purpose but to try to catch him in an inconsistency or falsehood — even a relatively minor one — that can then trigger a perjury charge.
Because there’s not a doubt in the world that Trump is a witness to any possible wrong-doing, the term doesn’t apply. WaPo believes this is the motivation:
Characterizing the president’s interview as a potential perjury trap is simply wrong. But it is of a piece with the broader effort by the president and his political allies to discredit Mueller’s investigation. It suggests — wrongly — that Mueller is treating the president unfairly. If the president commits perjury or false statements, it will be because he chose to lie — not because he was caught in a “trap.”
Or you can simply believe they’re all second-raters.