Republican Mitt Romney has appeared to question the character of US president Donald Trump.
Mr Romney, a former republican presidential nominee and recently elected Utah senator, said Mr Trump's "conduct over the past two years ... is evidence that the president has not risen to the mantle of the office."
The former Governor of Massachusetts will take his seat in the Senate when the session starts in the new year, having won 62.6% of the vote in Utah.
In an opinion piece published by the Washington Post, he had praise for some of Mr Trump's policy decisions, but added "With the nation so divided, resentful and angry, presidential leadership in qualities of character is indispensable.
"And it is in this province where the incumbent's shortfall has been most glaring."
Mr Romney says he does not intend to comment on every tweet by Mr Trump, but he promises to "speak out against significant statements or actions that are divisive, racist, sexist, anti-immigrant, dishonest or destructive to democratic institutions".