There is no way that Trump’s lawyers are going to allow him to risk his presidency. They know that Mueller is under extreme pressure from Democrats, NeverTrump Republicans, and the mainstream media to use the Russia investigation to oust Trump from office.
If Trump even forgets what day of the week it is, Mueller will be called upon to charge him. Indeed — given the political bias of his team — Mueller may even hope to do so.
It might be politically disastrous for Trump to refuse to cooperate with Mueller. But the most his lawyers are likely to allow him to do is to respond to written questions, with his answers closely vetted.
So Trump’s statement is likely just bluster to shape public perceptions — a tactic he has used before. Before the election, he vowed to fight the Trump University fraud case to the bitter end. After he won, Trump quietly settled the suit.
So, too, with the Mueller investigation. Trump wants the public to believe his innocence. But he does not want to have to fight for it in court.