The president did not say exactly what would trigger him to speak out, although he did sketch out a basic scenario.

White House press secretary Josh Earnest indicated Tuesday it is in part contingent on whether Trump obeys the “basic tenants and principles of American democracy,” including freedom of speech and religion.

But Earnest stressed that Obama’s “preference” isn’t to spend the bulk of his time disparaging his successor, saying the “institution of the presidency is not well served” when that occurs.

There are risks if Obama eventually decides to play Trump’s foil.

It would break with the decadeslong tradition of relative political silence for ex-presidents, a move that could damage his legacy and reputation.