WASHINGTON — After more than six years of less-than-heartfelt endorsements, a bitter parting of ways and a momentary rapprochement, the relationship between Mitt Romney and President Trump returned Wednesday to where it began: awkward, transactional and lingering uneasily between friend and foe.

One day after publishing a biting critique in The Washington Post that Mr. Trump “has not risen to the mantle of the office,” Mr. Romney declined to endorse the president’s re-election, saying he wanted to consider “alternatives” in 2020.

But Mr. Romney also made clear that, while he is willing to confront the president like few other Republican lawmakers, he had little appetite to spend his first months as Utah’s junior senator acting the part of Mr. Trump’s critic in chief.

“I don’t intend to be a daily commentator,” he said in an interview on CNN, repeatedly declining to escalate his attacks on the president and explaining that he would speak out against Mr. Trump only on issues of “great significance.”