Jeff Flake, a Republican, represented Arizona in the U.S. Senate from 2013 to 2019. He is a resident fellow at Harvard University and a contributor to CBS News.

Two years ago I stood in the Senate chamber and said: “There are times when we must risk our careers in favor of our principles.”

In my case, I had not supported the president’s election. One year into his presidency, I knew that I could not support his reelection. While I had hoped that I could still run for reelection to the Senate in 2018 as someone who would help to provide a check on the president’s worst impulses, it soon became apparent that this was not what Republican primary voters in my state were looking for. Whatever reservations they might have had when they voted for Donald Trump, one year into his presidency they wanted a senator who was all in.

But I already had seen too much. Traveling overseas I witnessed the damage being done to our standing in the world as a result of President Trump’s fondness for authoritarians and his scorn for allies. His hostility toward security alliances and trade agreements had placed our long-term security and our economy at risk. His adoption of the tyrant’s phrase “enemy of the people” put journalists in even greater peril, all over the world. His resentment toward refugees and profane description of certain countries were destroying generations of goodwill.

At home, I was convinced that his repeated disparagement of the judiciary, antagonism toward Congress and casual disregard for the truth were damaging our democratic institutions, and his persistent crudeness to his political opponents and cruelty toward vanquished foes were degrading our political culture. I knew that to have a chance of winning reelection, I would need to support policies I could not support and condone behavior I could not condone.

Now, two years later, it is my former Republican Senate colleagues who have a decision to make. Or, as I see it, two decisions to make. The first is difficult; the second is easy.

We have learned from a whistleblower that the president has abused the power of his office to pressure a foreign government to go after a political opponent. A rough transcript of the telephone call has removed all ambiguity about the president’s intent. In light of these revelations, the House of Representatives has launched an impeachment inquiry and will likely be forwarding to the Senate at least one article of impeachment.

Compelling arguments will be made on both sides of the impeachment question. With what we now know, the president’s actions warrant impeachment. The Constitution of course does not require it, and although Article II, Section 4 is clear about remedies for abuse of office, I have grave reservations about impeachment. I fear that, given the profound division in the country, an impeachment proceeding at such a toxic moment might actually benefit a president who thrives on chaos. Disunion is the oxygen of this presidency. He is the maestro of a brand of discord that benefits only him and ravages everything else. So although impeachment now seems inevitable, I fear it all the same. I understand others who might have similar reservations. The decision to impeach or not is a difficult one indeed.

Now for the easy decision. If the House decides against filing articles of impeachment, or the Senate fails to convict, Senate Republicans will have to decide whether, given what we now know about the president’s actions and behavior, to support his reelection. Obviously, the answer is no.

I am not oblivious to the consequences that might accompany that decision. In fact, I am living those consequences. I would have preferred to represent the citizens of Arizona for another term in the Senate. But not at the cost of supporting this man. A man who has, now more than ever, proved to be so manifestly undeserving of the highest office that we have.

At this point, the president’s conduct in office should not surprise us. But truly devastating has been our tolerance of that conduct. Our embrace of it. From the ordeal of this presidency, perhaps the most horrible — and lasting — effect on our democracy will be that at some point we simply stopped being shocked. And in that, we have failed not just as stewards of the institutions to which we have been entrusted but also as citizens. We have failed each other, and we have failed ourselves.

Let us stop failing now, while there is still time.

My fellow Republicans, it is time to risk your careers in favor of your principles. Whether you believe the president deserves impeachment, you know he does not deserve reelection.

Our country will have more presidents. But principles, well, we get just one crack at those. For those who want to put America first, it is critically important at this moment in the life of our country that we all, here and now, do just that.

Trust me when I say that you can go elsewhere for a job. But you cannot go elsewhere for a soul.