It won’t be easy in the months ahead being Mitt Romney, the highest-profile freshman Republican lawmaker in the 116th Congress. He will anger some people and frustrate many others. He will be called hypocritical as often as he is praised for criticizing President Trump. Ultimately, he may satisfy few people, but there’s little doubt that he will be a senator to watch.

All it took for this to come into sharp focus was the publication of an op-ed in The Washington Post that called into question the president’s fitness for office. It was not the first time Romney has called out Trump, but the timing raised eyebrows, coming on the eve of his swearing-in as Utah’s junior senator. What it means about things to come for Romney is much fuzzier.

The article set off Washington’s nonstop speculative machinery, with the conversation quickly pivoting to whether Romney might possibly challenge Trump for the GOP nomination in 2020 or make one more likely. The 2012 nominee tried to put to rest his intentions: “No, I’m not running again,” he told CNN’s Jake Tapper, noting that his previous run did not end well, in contrast, he said, to Trump’s victory in 2016.

His demurral about an endorsement of the president for reelection in 2020, however, suggested that Romney may believe that he could still play a role that would affect the future of the Trump presidency and the GOP. How that might happen is the question.

It won’t be by voting repeatedly against the president on the Senate floor. On most issues, particularly domestic policies, Romney and Trump are closely aligned, though on trade and foreign policy, they do part company.

Nor does Romney’s op-ed mean he will be a constant critic of the president. He will not, as he said to Tapper, be seeking a camera to respond every time the president says something outrageous. Given his personality, Romney probably will now step back to focus on becoming the business of becoming a senator. He will be hiring staff, joining committees, gaining knowledge of Senate procedures and doing the other things that all freshman senators do.

But his decision to step forward with an attack on the president suggests that he understands that he joins the Senate at what could be a particularly consequential moment, a time in which there will be a report from special counsel Robert S. Mueller III that could be damning to Trump and his presidency. Romney has a unique platform that comes with being a former presidential nominee. He no doubt knows he will be judged — and will judge himself — by how he uses it.

Predictably, Romney’s op-ed drew a swift response from the president, though it was far less angry than might have been assumed. Trump said he was “surprised he [Romney] acted so quickly” to go after him. He said, “I think he’s going to end up being a team player. . . . We’ll see what happens.” He said that, if Romney had fought the 2012 election against former president Barack Obama as hard as he is fighting against Trump now, “He would have won the election.”

On Twitter, reaction included praise from some Republicans, notably those who are in the Never Trump camp, and criticism from allies of the president, along with mocking and derision from many Democrats, who suggested that Romney, like some other elected Republicans who have been critical of Trump, would not back up his words with actions that would truly hold the president accountable.

The article also created a rift in the Romney family. Republican National Committee Chair Ronna McDaniel, who happens to be Romney’s niece but whose political loyalty these days is to the president, tweeted that her uncle’s op-ed was “disappointing and unproductive.” She accused Romney of doing the bidding of “Democrats and the media.”

Romney wanted his op-ed to land with force and so began with language designed to attract attention. “The Trump presidency made a deep descent in December,” he wrote. On that there is little disagreement, though there have been many other weeks and months of shocks and surprises. Still, December seemed even more unsettling than most other months, ending with a tweet by the president announcing an abrupt withdrawal of U.S. forces from Syria, which in turn triggered the resignation of Jim Mattis as secretary of defense.

In the op-ed, Romney’s sharpest language went to the issue of presidential fitness. “A president should demonstrate the essential qualities of honesty and integrity, and elevate the national discourse with comity and mutual respect,” he wrote. “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.”

Yet the article was in some ways a metaphor for the dilemma faced by all those Republicans who abhor the president’s behavior, who believe he is temperamentally unfit to occupy the Oval Office but who nonetheless support the conventionally conservative policies such as tax cuts, deregulation and even a border wall that the president has fought for. In other words, the op-ed started stronger than it finished.

“I will act as I would with any president, in or out of my party: I will support policies that I believe are in the best interest of the country and my state, and oppose those that are not,” Romney wrote. He said the same thing during his Senate campaign, and it is far from the kind of rallying cry that some Republican opponents of the president would like to see from a prominent leader of their party. It is also a reminder to Democrats that Romney, like others in the GOP who have been critical of Trump, is not about to become one of them.

The challenge for Romney is not to repeat the experience of retiring Sens. Bob Corker (Tenn.) and Jeff Flake (Ariz.), whose persistent criticism of Trump ultimately left them isolated in their party without seeming to influence Trump’s behavior. That isn’t the model, as some of those around Romney understand. But neither is the approach of retiring House Speaker Paul D. Ryan (R-Wis.), who had a platform and power but whose legacy has been tarnished by not having been a stronger counterforce to the president when it could have mattered most.

That means there is no easy path for someone like Romney and, on the basis of what he wrote and has said over the past 36 hours, no suggestion that he knows yet exactly how he will conduct himself, other than as a diligent senator representing his Utah constituents. He wanted to lay down a marker against Trump on his way into office, and he did. What comes next — and next and next — will prove to be the bigger test of his leadership.