Analysis by Chris Cillizza, CNN Editor-at-large

(CNN) -- The story of Mitt Romney and Donald Trump is long and complicated. And over the weekend, it added a new chapter.

In a Salt Lake Tribune op-ed headlined, "Where I stand on the Trump agenda," Romney, the front-runner for the seat that will be left vacant by Republican Sen. Orrin Hatch's retirement, made clear that if elected he would not walk in lockstep with Trump. Writes Romney:

"On one hand there are those who believe supporting the Trump agenda means supporting every policy the president proposes, whether or not they actually agree with that policy. It means refraining from criticizing anything the president says or does. The argument for this position is that you pick a team, so to speak, and when the leader of the team is criticized, his or her power to act is weakened and the opposition helped. So in order to achieve Republican policy aims, solid Republicans should stand with the president 100 percent, or at least stay silent when in disagreement.

"I take a different course. I will support the president's policies when I believe they are in the best interest of Utah and the nation."

It's impossible to separate that view from the recent political context as well as Romney's fraught relationship with Trump.

Romney's piece lands just weeks after Rep. Mark Sanford lost in a GOP South Carolina primary to a state legislator who had argued that Sanford's occasional criticism of Trump was a sign that he did not fully support the President. Earlier this year, Rep. Martha Roby was pushed into a Republican runoff in Alabama largely because she had distanced herself from Trump after the "Access Hollywood" tape came to light in the fall of 2016. (Weirdly, Trump endorsed Roby in the runoff race last week.)

Then there is Romney's past with Trump. When it became clear that Trump had a real chance to be the GOP nominee in 2016, Romney delivered an absolutely blistering takedown of the GOP businessman. Here's one of the many scathing bits:

"There's plenty of evidence that Mr. Trump is a con man, a fake. Mr. Trump has changed his positions not just over the years, but over the course of the campaign. And on the Ku Klux Klan, daily for three days in a row."

Trump, of course, responded -- and responded and responded. "Failed presidential candidate Mitt Romney, the man who 'choked' and let us all down, is now endorsing Lyin' Ted Cruz," he tweeted in March 2016. "This is good for me!" In June 2016, Trump added this: "Mitt Romney had his chance to beat a failed president but he choked like a dog. Now he calls me racist-but I am least racist person there is."

Then somehow things got better.

The next tweet Trump sent after that one attacking Romney as a choking dog came that November 13 and said: "Mitt Romney called to congratulate me on the win. Very nice!" Then the two men met for dinner -- amid talk that Trump might pick Romney as his secretary of state. In the wake of that meeting, Romney sounded like a different person than the man who had savaged Trump the previous spring.

"We had another discussion about affairs throughout the world and these discussions I've had with him have been enlightening, and interesting, and engaging," Romney said of the dinner. "I've enjoyed them very, very much."

Ahem. Then Trump didn't pick Romney. And Trump urged Hatch not to retire. And Hatch retired anyway. And Romney decided to run. And Trump endorsed him. "@MittRomney has announced he is running for the Senate from the wonderful State of Utah," Trump tweeted in February. "He will make a great Senator and worthy successor to @OrrinHatch, and has my full support and endorsement!"

Which, broadly speaking, brings us up to the present day -- and Romney's attempt (again) to find some sort of acceptable distance from Trump. This op-ed is less brave than it might initially appear -- for two main reasons:

1. Utah's Republican Party has never cottoned to Trump. In the state's presidential primary, Trump came in third -- winning just 14%. And while Trump carried the state in November, he did so with just 45%, 28 points worse than Romney did in the Beehive State in 2012.

2. The Republican primary in Utah is on Tuesday. Romney faces no real threat to his chances and it's hard to imagine an op-ed written the weekend before the primary race would give the hardcore Trump loyalists enough time to organize against Romney.

Still. Trump is not one to overlook a slight -- even one as minor as saying that you may not agree with him 100% of the time.

"People ask me why I feel compelled to express my disagreements with the president," writes Romney in the op-ed. "I believe that when you are known as a member of a 'team,' and the captain says or does something you feel is morally wrong, if you stay silent you tacitly assent to the captain's posture."

Over to you, Donald.