WASHINGTON (AP) — It's hard to refer to someone as "Hitler" and end up in their good graces, let alone potentially become the person they choose to help lead the country.

But Ohio Sen. JD Vance's shifting position on Donald Trump over the years from onetime critic of the former president to staunch ally is a metamorphosis shared by many of Trump's potential running mates.

It's not unheard of for a running mate to move beyond past disagreements with a presidential candidate.

Joe Biden had a notably barbed exchange with Kamala Harris in 2020 when both were seeking the Democratic nomination. Biden picked her to be his vice president anyway.

But the shift is more striking for Trump's potential running mates, in some cases requiring them to abandon long-held policy positions and recant vehement criticism.

Here's a look at some of those shifts:

JD Vance

In a 2016 interview with Charlie Rose while promoting his book "Hillbilly Elegy," Vance called himself "a Never Trump guy" and said of the soon-to-be-president, "I never liked him."

He told NPR that year, "I can't stomach Trump." He wrote an op-ed for The New York Times titled: "Mr. Trump Is Unfit For Our Nation's Highest Office."

Vance said he didn't vote for Trump in 2016 and his former roommate shared images of a text message Vance sent him that year in which he called Trump "cynical" and said he could be "America's Hitler."

But by the time Vance launched his campaign for Senate in 2021, his views were closely aligned with Trump's. He met with the former president and quickly won his endorsement, gaining a crucial boost in the Republican primary.

Vance has said he "was wrong" about Trump. In an interview this month on Fox News Channel, he was asked to explain his past criticism.

"I didn't think he was going to be a good president," Vance said. "He was a great president. And it's one of the reasons why I'm working so hard to make sure he gets a second term."

Marco Rubio

Some of the Florida senator's harshest comments about Trump came as they sparred during the 2016 race. Trump started calling him "Little Marco" and mocking him. Rubio insulted Trump's makeup and the size of his hands.

Rubio called also called Trump a "con artist," and "the most vulgar person to ever aspire to the presidency."

This year, when ABC News played back some of Rubio's comments from 2016, he responded by saying, "It was a campaign."

He made similar comments to CNN, saying "That is like asking a boxer why they punched somebody in the face in the third round. It's because they were boxing."

Their relationship improved dramatically while Trump was in the White House. And as Trump has campaigned for the presidency a third time, Rubio has cheered his proposals.

In the Senate, Rubio had long been a prominent voice on immigration and was a key member of a group that worked on a 2013 bill that included a path to citizenship for millions of people in the country illegally. Now, Rubio says he support's Trump's plan to deploy the U.S. military to deport those in the country illegally.

Doug Burgum

The North Dakota governor ran against Trump this year, but dropped out in December and endorsed Trump before voting began.

Before that, Burgum had rejected the idea of partnering with Trump.

In an interview last July on NBC's "Meet the Press," Burgum, a businessman, was asked if he would ever do business with Trump, and responded, "I don't think so." He added, "I just think that it's important that you're judged by the company you keep."

The next month, he told CNN in an interview that he would not serve as Trump's vice president.

Burgum this year has become an enthusiastic champion of Trump and has leveraged his profile as a wealthy businessman and governor versed in energy policy to help the Republican secure millions in fundraising, especially from high-dollar donors.

Elise Stefanik

When the New York congresswoman was first elected in 2014, she was known as a moderate Republican with ties to the party's establishment.

In 2016, she initially supported Ohio Gov. John Kasich's campaign. When Trump was the party's nominee, she didn't say his name, only saying she would "support my party's nominee in the fall."

She became a more vocal supporter as the election neared but made it clear she disagreed with him at times. Those disagreements faded over the years.

Stefanik emerged as one of Trump's most outspoken defenders during his first impeachment in 2019, and it's a role she's embraced ever since. When Republicans ousted former Rep. Liz Cheney from leadership over her criticism of Trump and his efforts to overturn the 2020 election, it was Stefanik they chose to take her place.

Her loyalty to Trump stood out in 2022, as the former president's esteem within the party had deflated after he was absorbing blame for weaker-than-expected results in the midterm elections. Stefanik announced days after the election that she was endorsing Trump for president in 2024 — an announcement that came before Trump even said he was running.

Tim Scott

In 2016, the South Carolina senator initially backed Rubio in the presidential race and excoriated Trump for his reluctance to condemn the Ku Klux Klan.

"If Donald Trump can't take a stand against the KKK, we cannot trust him to stand up for America against Putin, Iran or ISIS," said Scott, the Senate's only Black Republican.

Scott still supported Trump in the 2016 election against Democrat Hillary Clinton, calling him the "lesser of two evils."

Scott also criticized Trump after his comments equivocating about the 2017 white nationalist rally in Charlottesville, Virginia, saying that his "moral authority" was "compromised." He met with Trump at the White House after. In an interview on Fox News Channel on Thursday, Scott said that he shared his perspective with the then-president in that meeting and from then on they worked to "find solutions together."

"It was the Charlottesville incident that made our relationship what it is today," Scott said.

Though he ran against Trump in the 2024 GOP primary, Scott dropped out and has become one of his most enthusiastic cheerleaders.