In a letter to the public of September 18, 2024, 111 former Republican national security officials who served in GOP administrations dating back to the Reagan presidency, together with former Republican members of Congress, endorsed Vice President Kamala Harris for President.¹ The letter was issued after former Bush VP Dick Cheney and his daughter, former Congresswoman Liz Cheney, had endorsed Harris.² In a letter of August 26, 2024, 200 Republicans who had worked for George W. Bush or presidential candidates John McCain or Mitt Romney also declared that they would be voting for Harris and Governor Tim Walz.³

The GOP officials and members of Congress wrote on September 18 that although they disagreed with Harris on many issues, Trump had manifested "dangerous qualities" including "unusual affinity" for Russian President Vladimir V. Putin and other dictators and "contempt for the norms of decent, ethical and lawful behavior."⁴ They added that during his presidency, "he promoted daily chaos in government, praised our enemies and undermined our allies, politicized the military and disparaged our veterans, prioritized his personal interest above American interests and betrayed our values, democracy and this country's founding documents."⁵

The 200 Republican signers of the August 26 letter wrote: "At home, another four years of Donald Trump's chaotic leadership, this time focused on advancing the dangerous goals of Project 2025, will hurt real, everyday people and weaken our sacred institutions." They further declared: "Abroad, democratic movements will be irreparably jeopardized as Trump and his acolyte JD Vance kowtow to dictators like Vladimir Putin while turning their backs on our allies. We can't let that happen."⁶

Among several other prominent Republicans who have characterized Trump as severely deficient in character and competence was Senate majority leader Mitch McConnell. McConnell's observations of Trump were quoted in a book to be published on October 29, 2024, by Michael Tackett, the deputy Washington bureau chief of the Associated Press, to be published Oct. 29. McConnell considered Trump to be "a narcissist," "stupid," and "a despicable human being."⁷

General Mark Milley, who served as chair of the Joint Chiefs of Staff from 2019 through 2023, having been picked by Trump for that position, the highest US military office, viewed the possibility of Trump returning to power with alarm. General Milley told acclaimed Washington Post journalist Bob Woodward in March 2023 that Trump is "dangerous" and "a fascist to the core."