Fifty of the nation's top Republican national security officials signed a letter Monday declaring that they will not vote for Donald Trump, calling him unfit for the presidency. They noted that Trump “lacks the character, values and experience” to be president and “would put at risk our country’s national security and well-being.” Peter Feaver—professor of political science and public policy at Duke and former director for Defense Policy and Arms Control on the National Security Council in the Bush White House—was among the signatories, which also included many former top aides or cabinet members for President George W. Bush. The Chronicle sat down with Feaver to discuss his decision to sign the letter and his role in the 2016 election.

The Chronicle: How did the letter come about? What was the process behind writing it and acquiring the signatures for it?

Peter Feaver: John Bellinger [who served as the Legal Adviser for the U.S. Department of State and the National Security Council during the George W. Bush administration] organized this. He and I have communicated about this over the last month. He wanted this to be a letter just for Republican national security specialists who had served at a relatively high rank in previous administrations to distinguish it from the earlier letter in March organized by Eliot Cohen, which was available to any national security specialist who consider him/herself to be a Republican.

TC: Was there a moment when you realized that you couldn't support Trump?

PF: I have opposed Trump ever since he started running for President last summer. At that point, the decision was easy since there were over a dozen Republican candidates manifestly better to lead the country. As the year has progressed, Trump's political power has grown, but he has not improved on any of the dimensions that concerned me last year: his temperament, his integrity, his understanding of complex issues, his capacity to attract the nation's finest talent and mobilize them to address our challenges.

TC: Have you gotten any pushback from your friends in the GOP for this decision? Are any of your colleagues supporting Trump?

PF: There is a lively and painful debate among my friends in the GOP. I have friends who run the gamut from early and enthusiastic supporters of Trump all the way to those who have (or will) publicly endorse Hillary Clinton, and every shade of position in between. There is a very principled position that I understand and respect, but is different from mine: that some quality advisors should not publicly denounce him so as to be available to staff his administration should he win. I understand that position, and I do hope that if he wins he will somehow assemble a team that can mitigate the things I worry about. I recognize that by signing this letter I am making it impossible for me to serve in that capacity. It is an individual decision, and I respect those who have carefully reflected and come to a different position than I have.

TC: Some media outlets have said that many Trump voters and Trump himself will not care about the letter. Do you think this is the case? What did you hope to accomplish through the letter?

PF: I think it won't influence his hardened base, although it might on the margins influence those who are undecided. I do think there is some chance that this letter has strengthened the hand of Republican leaders who are trying to get Trump to behave more responsibly on national security issues. They still have some influence on him, and while the Trump campaign predictably denounced all the letter-signers as knaves and worse, in fact the knowledgeable people in Trump's circle know the opposite is true. In fact, quite a number of the folks on that list were recruited by the Trump campaign earlier in the year.

TC: You’ve expressed your support for Republican candidates in the past. Who do you plan to vote for this year, if not Trump?

PF: The letter quite explicitly does not endorse Secretary Clinton, although some on that list do intend to publicly endorse her and vote for her. I do not. It is important for Republicans to focus on down ballot elections for the Senate and House. Not voting for Trump does not mean not voting.

TC: You’ve contributed to the campaigns of Republican candidates in the past, so will you contribute to the campaigns of Trump’s opponents if he is as dangerous as you say he is?

PF: It is important that Republicans focus on the down-ticket races for the Senate and the House.

TC: Former Acting CIA Director Michael Morell recently called Trump “an unwitting agent of the Russian Federation.” Do you agree with his reasoning and his conclusion?

PF: Morell is using a particular term of art that basically means Trump's actions and statements are benefiting Putin's strategy more than they are benefitting American interests. Understood that way, I think it is a defensible critique.

TC: You’re an expert on nuclear weapons and civil-military relations. Do you think the world will be in significant danger if Donald Trump is in control of the U.S. nuclear arsenal as his opponents have suggested?

PF: Some of the media discussion of this has been hyperbolic. There are multiple safeguards built into the nuclear command and control system. It is not accurate to say that a President Trump could fire off a nuclear weapon as recklessly as he can fire off a tweet. However, it is the case that in a crisis, for instance with a nuclear-armed North Korea, Trump's temperament could be problematic and could lead to dangerous escalation whereas another President with better self-control might be able to manage it more safely.

TC: How else have you been involved in this election? How are you supporting or opposing candidates?

PF: I was part of an organization, the John Hay Initiative, that has been available to advise any candidate on foreign policy. This organization provides fact sheets and position papers on myriad issues and most of the presidential candidates on the Republican side took advantage of this group to become better informed on key issues. I also was part of Jeb Bush's national security team.

TC: What do you think the odds of Trump winning the election are?

PF: The political science models give Clinton a decided edge. But she is a uniquely vulnerable candidate in ways the models do not capture well. I think there is definitely a chance Trump could win.

TC: Would you serve in a Trump administration if asked to provide your foreign policy expertise for the benefit of the country?

PF: Because I signed the letter I am quite certain I would not be asked to serve. That said, in the hypothetical that there is a Trump Administration and some member of his team asked me for advice on my areas of expertise, of course I would supply that. I have provided advice and informal input to every administration for the past 25 years whether or not I supported that President in the election.

TC: Do you have any idea what others who signed the letter would do?

PF: I think we are all in the same boat.

TC: Do you think Trump is already hurting U.S. foreign policy and to what extent?

PF: Trump's reckless statements and erratic behavior on the campaign trail have already hurt U.S. foreign policy to a certain extent. He has confused and demoralized our allies and partners and he has emboldened those around the world who wish to see America made weaker. The point of this most recent letter is that this damage could increase dramatically if he became President and had at his disposal the great power of that office. Every one of the letter-signers has advised a President on a critical policy or in a dangerous crisis and we all know how important qualities like temperament, judgment, integrity and analytical rigor are in those cases.

Editor's note: This interview was conducted via email. Gautam Hathi and Rachel Chason contributed reporting.