Story highlights Julian Zelizer: Secretary of state can exert significant influence in only one way

Resign on principle, explain Trump White House must change course, he says

Julian Zelizer is a history and public affairs professor at Princeton University and the author of "The Fierce Urgency of Now: Lyndon Johnson, Congress, and the Battle for the Great Society." He's also the co-host of the "Politics & Polls" podcast. The opinions expressed in this commentary are his own.

(CNN) If Secretary of State Rex Tillerson is unhappy with the way that President Donald Trump is conducting his White House, he should resign, and he should do so soon and in a very public way.

Over the past few weeks there has been growing evidence that Tillerson disapproves of Trump's performance in office. The secretary, who arrived at Foggy Bottom without any government experience or a close connection to Trump, has been forced to sit on his hands as the President has marginalized him, criticized him and moved in a different direction on key issues such as North Korea than the cautious former oil executive would seem to prefer.

Tillerson has tried to clean up Trump's messes, but to little avail. In what some have compared to a hostage video, the secretary had to take questions on camera this week after stories emerged on NBC that he had seriously considered resigning in July and had called the President a "moron."

It might be true, as Senate Foreign Relations Chairman Bob Corker told the press, that Tillerson is one of the few people protecting the United States from total chaos. But it is not certain that staying in the job is actually making things better. In fact, there is an argument to be made that, if Tillerson really is unhappy, the best thing he could do is to undertake a major act of political courage by leaving the administration and triggering the kind of ripple effect on Capitol Hill urgently needed to wake Republicans from their politically induced slumber.

There have been a few Cabinet and other senior officials who have resigned in protest over the years. Secretary of State William Jennings Bryan left President Woodrow Wilson's administration in 1915 because he felt the administration was taking an unnecessarily militaristic path in Europe.

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