"Nor do I think that the Romney type of establishment, big government Republicanism is popular enough to win a general election".
In it, he said Mr Trump's conduct since being elected in 2016 "is evidence that the president has not risen to the mantle of the office".
Romney remains a quintessential establishment Republican insider in the mold of former Arizona Senator Flake, former Tennessee Senator Bob Corker, and former Ohio Governor John Kasich.
In a letter Tuesday night to the other 167 committee members, Jevon O.A. Williams warned that Romney could use "loopholes" in the nominating process to challenge Trump, the Daily Mail of London reported.
A passing reference to Brexit was also made, with Mr Romney calling for a "a unified and strong Europe, not a disintegrating union".
The Post reported a year ago that Trump himself had "lightheartedly" requested she make the change before she got the RNC job.
Baker Mayfield of Cleveland Browns fined
After the Browns stopped the Ravens on defense, Mayfield led the Browns downfield near field-goal range before linebacker C.J. He finished this season with five 100-yard games, including 185 yards on 14 catches in last week's loss at New Orleans.
In the op-ed, Romney said many of Trump's policies - on taxes, deregulation, confronting China on trade and appointing conservative judges - have been longtime Republican goals.
This speech, perhaps one of the most critical ones about Trump from a current GOP member, led political analyst and Fox News commentator Bill Kristol to brand it a sign of growing resistance to the 45th U.S. president from within his own party. "And it is in this province where the incumbent's shortfall has been most glaring", Romney writes in a Washington Post op-ed.
McDaniel retweeted Trump's remarks about Romney and added that the president is constantly "attacked and obstructed" by the media and Democrats.
"The world needs American leadership, and it is in America's interest to provide it", he wrote. "A world led by authoritarian regimes is a world - and an America - with less prosperity, less freedom, less peace".
McDaniel joins a number of fellow prominent Republicans, including Trump, who are condemning Romney's decision to publish the piece less than 48 hours before he is sworn into the Senate. "Be a TEAM player & WIN!" It would be tricky terrain for Sasse to publicly battle with Trump, who won the state in 2016 by 25 percentage points.
When he announced his run for senator, Romney appeared to take a veiled swipe at the Trump administration's immigration policies. Jeff Flake (R-AZ), Trump told Romney to stop attacking him and "be helpful" to his presidency. And on Wednesday morning, Trump addressed Romney's words with a single 280-character tweet, saying he should be happy "for all Republicans".
"I don't intend to be a daily commentator", Romney said, noting he won't always seek out cameras in the Senate, but "if it's a matter of great significance, I will speak out".
The barbed remarks from the 2012 Republican presidential candidate came as he and other lawmakers prepare take up their seats in the new Congress.