Bernie Sanders
Sen. Bernie Sanders says he has no choice but to call President Trump out as a liar. Above, Sanders mocks President Donald Trump with inauguration crowd photos, Feb. 25, 2017. Reuters/Kevin Lamarque

Sen. Bernie Sanders published an essay Tuesday defending a series of tweets he sent Monday accusing President Donald Trump of lying — repeatedly.

"How does one respond to a president who has complete disregard for reality and who makes assertions heard by billions of people around the world that have no basis in fact?" Sanders, I-Vt., asked in an essay full of rhetorical questions that was published on Medium.

The essay, titled "What should we do if the president is a liar?" was written in response to an Amber Phillips column published in the Washington Post on Monday.

Phillips used five Sanders tweets to illustrate "the state of our political discourse right now" and point out "there are no rules right now in politics about what you can/can't or should/shouldn't say." Phillips also criticized President Trump for making "several eyebrow-raising claims" about voter fraud and wiretapping.

Sanders said he happens "to strongly believe in civil political discourse," but asked what other choice is there when confronted with a president who continuously lies.

"Do we make a bad situation worse by disrespecting the president of the United States? Or do we have an obligation to say that he is a liar to protect America’s standing in the world and people’s trust in our institutions?" Sanders asked.

"One of my great concerns is that there undoubtedly will be major crises facing the United States and the global community during Trump’s tenure as president. If Trump lies over and over again, what kind of credibility will he, or the United States, have when we need to bring countries around the world together to respond to those crises? How many people in our country and other countries will think that Trump is just lying one more time?"