Rubio, at the time one of the GOP’s brightest, rising stars, frequently referred to Trump as a “con artist” with “small hands.” In the present day, Rubio has realigned himself to be one of the president-elect’s top surrogates, campaigning for Trump’s 2024 bid in the final days of his campaign.

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“Donald Trump, a con artist, will never get control of this party,” he declared at a 2016 campaign rally in Dallas, Texas. “Friends don’t let friends vote for con artists.”

But after being dubbed “Little Marco” by then-candidate Trump, Rubio’s polling plummeted, and he eventually endorsed Trump at the 2016 Republican National Convention.

In a video message at the 2016 convention, Rubio called for the party to “come together and fight for a new direction for America” while praising Trump for his ideas on taxes, the military, and appointing conservative judges.

But Rubio’s transformation from one of Trump’s most vocal detractors to one of his key supporters was on full display in the final stretch of the 2024 cycle.

Appearing at Trump’s Allentown, Pennsylvania rally shortly after a joke told at his Madison Square Garden rally by a comedian sparked controversy, Rubio fiercely defended the Republican nominee.

Rubio, who spoke in Spanish as Allentown has a heavily Puerto Rican community, said Trump has the most “fascinating, most diverse coalition of Americans from every race, every ethnicity, every walk of life in modern American political history.”

He continued, “It reminds us too that American … has never been a skin color, American has never been where your parents are born… American is anyone who is here, who wants to move this country forward and believes that our rights come from God, family’s more important than government and this is the greatest country in the history of the world,” Rubio said in a nod to the country’s immigrant roots.

Despite the rocky start to their relationship, the two politicians’ relationship started defrosting during Trump’s first administration, with Rubio becoming something of an informal adviser on foreign policy, specifically involving South and Central America and China.

John Bolton, Trump’s former national security adviser, said in an interview with USA Today that Rubio’s straightforward focus on policy ingratiated him to the Trump team.

“Rubio and Trump seemed to have a good personal relationship, and Marco just made the case very calmly and persuasively,” Bolton claimed. “I think it did have an effect on Trump.”

Marc Short, former Vice President Mike Pence’s chief of staff, added that Trump “always embraces converts” and noted that Rubio “was somebody who was always eager to work with the administration.”

According to Trump world insiders, the president-elect and Rubio further strengthened their relationship over the summer.

Rubio had been on Trump’s shortlist for vice president, but, even after that position went to Sen. J.D. Vance (R-OH), he campaigned heavily for the president-elect through Election Day.

And senior members of Trump’s team told the Washington Examiner that, on the trail, the two leaders quickly bonded over their shared love of sports.

“I think President Trump and Sen. Rubio realized they’re much more alike than they thought,” one Trump insider explained. “Spending time together on the campaign trail, they were able to get to know each other on a personal level and just take the politics out of it. President Trump realized that [Rubio] is the exact type of leader we need to take on China.”

“This guy practices what he preaches,” a second Trump insider said of Rubio, noting that the senator has twice been personally sanctioned by the Communist Party of China. “President Trump was very impressed by his attitude toward Beijing, and he has experience working with Democrats to reset the U.S.-China relationship.”

“Marco is a Highly Respected Leader, and a very powerful Voice for Freedom,” Trump wrote in his Rubio announcement. “He will be a strong Advocate for our Nation, a true friend to our Allies, and a fearless Warrior who will never back down to our adversaries. I look forward to working with Marco to Make America, and the World, Safe and Great Again!”

Rubio remains one of Trump’s only Cabinet nominations so far who has seen support from both sides of the aisle.

Sen. John Fetterman (D-PA) announced that he would vote to confirm Rubio before Trump had even made the nomination official.

“Our politics are different, but he’s a serious guy, and he’s a really great pick,” Fetterman told the Washington Examiner. “They wouldn’t be my picks, but I want to embrace and vote for the people like Rubio, Stefanik, and then there’s others that I probably wouldn’t agree with it, but I’m not going to be in the business now to just start dumping on everybody.”

Sen. Mark Warner (D-VA), the chairman of the Senate Intelligence Committee, told the Washington Examiner that Rubio is a “very strong choice” before offering him a full endorsement in a statement.

“I have worked with Marco Rubio for more than a decade on the Intelligence Committee, particularly closely in the last couple of years in his role as Vice Chairman, and while we don’t always agree, he is smart, talented, and will be a strong voice for American interests around the globe,” he wrote.

Though most Republicans are getting in line behind Rubio’s nomination, some have reportedly expressed concerns about his hawkish past, including Trump’s nominee to be Secretary of Health and Human Services, Robert F. Kennedy Jr.

Rubio’s nomination sets off a chain of political dominoes. If confirmed, Gov. Ron DeSantis (R-FL) will be forced to pick a temporary replacement until that seat comes up for election in the 2026 cycle.

A number of Trump allies, like Elon Musk, have suggested that Lara Trump, the president-elect’s daughter-in-law and a co-chair of the Republican National Committee, be selected to fill Rubio’s seat.

Rep. Anna Paulina Luna (R-FL) said earlier this week that Lara Trump would be the “perfect fit” to replace Rubio.

“I think Lara Trump would avoid a really nasty primary in two years when that seat then comes open,” she said in an interview with conservative podcaster Benny Johnson. “And I think that she has the qualification. She proved herself, not just as a national leader, but also as a stateswoman.”

Furthermore, depending on how the next four years go, Rubio might be able to launch a second presidential campaign of his own, though Vance would expected to launch a 2028 run as well.

“I think if anyone can pose a serious threat to Vice President Vance, it would be Rubio,” one senior Trump official told the Washington Examiner. “He has an opportunity to win over MAGA. It’s really up to him how that goes.”