While Mr McMaster said he doesn’t “support anybody” in the next presidential cycle – citing his penchant as a national security official to “steer clear of politics” – he could not bring himself to throw his weight behind Mr Trump because of how polarising he is.
"No, I think it would be terribly divisive," McMaster said in an interview with CNN’s Jake Tapper on Sunday.
Mr McMaster would not comment on whether the Senate should vote to convict Mr Trump at his upcoming impeachment trial, a move that would allow senators to bar him from ever holding federally elected office again.
But Mr McMaster did say the president’s impeachment in the House over his role inciting the insurrection at the US Capitol on 6 January that resulted in five deaths was proof “nobody is above the law”.
Mr McMaster joins a chorus of Republican leaders previously allied with Mr Trump who have denounced his actions since losing the 2020 election – culminating in the deadly riots earlier this month as Congress was certifying Joe Biden’s electoral victory – and questioned the president’s future role in the party.
Even the typically pro-Trump Republican governor of Arkansas, Asa Hutchinson, admitted on Sunday that Mr Trump bears at least some blame for raising the political tensions that snapped on 6 January.
“He asked all the people to come to Washington for the rally and then he used very aggressive language in the rally itself and he misled people as to what happened during the election, that it was stolen and that our checks and balances are not working,” Mr Hutchinson said in an interview with Chris Wallace of Fox News Sunday.
The president’s persistent challenge to the 2020 was “wrong” for deluding his supporters into thinking he could actually remain in power, Mr Hutchinson said.
Such gaslighting “did not serve our nation well, and it was demonstrated on January 6”, the governor said.
Several of Mr Trump’s top advisers and Cabinet officials have resigned in the final days of his presidency in protest against his post-election actions.
They include such high-profile names as Transportation Secretary Elaine Chao, who is married to Senate Republican Leader Mitch McConnell, and Education Secretary Betsy DeVos.