Since Donald Trump first endorsed Mitt Romney’s presidential candidacy during an uncomfortable news conference at the Trump International Hotel & Tower Las Vegas in February 2012, both businessmen-turned-politicians have taken aggressively contradictory stances on the issue of immigration, and lambasted one another for positions they themselves once espoused.

In an op-ed in The Washington Post suggesting that President Trump’s “divisive, racist, sexist, anti-immigrant, dishonest” actions and statements have marked a steep descent in American politics, Romney shifted the long-simmering feud between himself and Trump into offensive gear. The president’s response, urging Romney to be a “team player” by supporting his hardline immigration agenda, have embroiled both politicians in an avoidable contretemps before the newest Congress has even been seated.

More revealingly, however, the fight has invited closer scrutiny of both Romney and Trump’s frequent flip-flops on the issue of immigration—and each other. The Romney-Trump relationship has waxed and waned numerous times since 2012, when the presidential hopeful accepted Trump’s endorsement at the height of the latter’s propagation of the racist “birther” conspiracy theory that President Barack Obama was not born in the United States.

But after Romney failed to unseat Obama in the 2012 presidential election, Trump’s criticism of Romney came from an entirely different—and entirely pro-immigrant—direction.

“Republicans didn’t have anything going for them with respect to Latinos and with respect to Asians,” Trump told NewsMax reporter Ronald Kessler two weeks after the election, calling Romney’s proposed policy of “self-deportation” of undocumented immigrants from the United States “maniacal.”

“The Democrats didn’t have a policy for dealing with illegal immigrants, but what they did have going for them is they weren’t mean-spirited about it,” Trump said. “He lost all of the Latino vote. He lost the Asian vote. He lost everybody who is inspired to come into this country.”

To win in 2016, Trump continued, the Republican Party had to develop a comprehensive immigration policy that would allow for the “people wanting to be wonderful productive citizens of this country.”

Romney himself has shifted positions on the immigration issue multiple times—even running to the right of Trump during his bid to replace Hatch last year.

“I’m also more of a hawk on immigration than even the president,” Romney said at a question-and-answer session in March. “My view was these DACA kids shouldn’t all be allowed to stay in the country legally.”

Ever one to change direction in favor of prevailing political winds—over the course of his three-decade political career, Romney has described himself as everything from an independent to “severely conservative”—the former Republican presidential nominee said during his Senate run that Trump’s temporary willingness to include a pathway to citizenship for roughly 1.8 million recipients of the Deferred Action for Childhood Arrivals program meant that he “was more conservative than others in my party.”

Unlike Trump, “I draw the line and say, those who’ve come illegally should not be given a special path to citizenship,” Romney said.

Trump, of course, later went on to actually win the 2016 presidential election on the most anti-immigrant platform of any candidate since Millard Fillmore.

With the op-ed, Romney made an early bid to fill not just the seat of outgoing Utah Sen. Orrin Hatch, but that of retiring Sen. Jeff Flake, the Senate’s highest-profile Republican critic of President Donald Trump. The former Massachusetts governor singled out Trump as “promot[ing] tribalism by exploiting fear and resentment,” and declared that the president’s low moral character and conduct in office “is evidence that the president has not risen to the mantle of the office.”

In response, the president noted on Twitter that Romney failed to win the White House in 2012, despite his own endorsement of Romney’s candidacy, and that he would prefer Romney’s time in Congress be spent fighting for his border wall over criticizing the Trump administration.

“I wish Mitt could be more of a team player,” Trump told reporters on Wednesday in the Oval Office. “I endorsed him and he thanked me profusely.”