Republican U.S Senate candidate Mitt Romney during the 2012 presidential race. Romney won the race to replace retiring Utah Republican Senator Orin Hatch who has been in the Senate for over 41 years. George Frey/Getty Images

In an op-ed for The Washington Post, the former Republican presidential candidate and incoming US senator, Mitt Romney says US President Donald Trump has failed to live up to the office of the presidency.

Some Trump policies are acceptable, but its is the president's character - or lack of it - that has hurt the United States, Romney wrote.

"To a great degree, a presidency shapes the public character of the nation. A president should unite us and inspire us to follow 'our better angels.'"

But this is where Trump is at his worst, Romney says.

In an op-ed for The Washington Post, the former Republican presidential candidate and incoming US senator, Mitt Romney says Trump has failed to live up to the office he was elected for.

Some Trump policies could work, but it is the president's character - or lack of it - that has hurt the United States, Romney, wrote on Wednesday.

"To a great degree, a presidency shapes the public character of the nation. A president should unite us and inspire us to follow "our better angels.""

But this is where Trump, and therefore America, is falling down, Romney claims.

"As a nation, we have been blessed with presidents who have called on the greatness of the American spirit. With the nation so divided, resentful and angry, presidential leadership in qualities of character is indispensable," Romney said.

"And it is in this province where the incumbent's shortfall has been most glaring."

Romney pointed out the weight of global respect for a US under Trump has been falling quickly and with it a cost in allies and authority that accompanies reliable leadership.

"To reassume our leadership in world politics, we must repair failings in our politics at home. That project begins, of course, with the highest office once again acting to inspire and unite us," Romney said.

According to Romney, the Trump presidency fell to new lows in December, hit as it was by losses of experience in Defense Secretary Jim Mattis and White House Chief of Staff John F. Kelly.

But it was the sealing appointment "of senior persons of lesser experience," and the jettison of willing allies that hurt the nation more, he said.

"The president's thoughtless claim that America has long been a "sucker" in world affairs all defined his presidency down," Romney said.

"It is well known that Donald Trump was not my choice for the Republican presidential nomination. After he became the nominee, I hoped his campaign would refrain from resentment and name-calling."

"It did not," he lamented.

In a nutshell, Trump's behavior over the past two years, and particularly his actions in December are proof "that the president has not risen to the mantle of the office," Romney asserted.

Romney, a Republican from Utah and the party's 2012 nominee for president, will be sworn into the Senate on Thursday and emphasized his willingness to work with both the White House and fellow senators to achieve policy change.

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