Fifty former national security officials who "served in senior national security and/or foreign policy positions in Republican Administrations, from Richard Nixon to George W. Bush" have vowed never to vote for Donald Trump.

The group, which published an open letter earlier Monday, saying:

From a foreign policy perspective, Donald Trump is not qualified to be President and Commander-in-Chief. Indeed, we are convinced that he would be a dangerous President and would put at risk our country's national security and well-being. Most fundamentally, Mr. Trump lacks the character, values, and experience to be President. He weakens U.S. moral authority as the leader of the free world. He appears to lack basic knowledge about and belief in the U.S. Constitution, U.S. laws, and U.S. institutions, including religious tolerance, freedom of the press, and an independent judiciary. In addition, Mr. Trump has demonstrated repeatedly that he has little understanding of America's vital national interests, its complex diplomatic challenges, its indispensable alliances, and the democratic values on which U.S. foreign policy must be based. At the same time, he persistently compliments our adversaries and threatens our allies and friends. Unlike previous Presidents who had limited experience in foreign affairs, Mr. Trump has shown no interest in educating himself. He continues to display an alarming ignorance of basic facts of contemporary international politics. Despite his lack of knowledge, Mr. Trump claims that he understands foreign affairs and "knows more about ISIS than the generals do."

Among those who signed the letter are former DHS secretary Michael Chertoff, Former CIA and NSA director Michael Hayden, former DHS secretary Tom Ridge, and John Negroponte, who served as the Director of National Intelligence.

While the group's signatories aren't supporting Trump, it's not clear how many, if any at all, Hillary Clinton was able to poach. The group writes:

We understand that many Americans are profoundly frustrated with the federal government and its inability to solve pressing domestic and international problems. We also know that many have doubts about Hillary Clinton, as do many of us. But Donald Trump is not the answer to America's daunting challenges and to this crucial election. We are convinced that in the Oval Office, he would be the most reckless President in American history.

You can read the whole letter here.