With former President Donald Trump getting closer to announcing his vice presidential pick, many of the top contenders for the job have a long history of attacking him personally and politically.

As Trump gears up to take on President Joe Biden in what's expected to be a very close race in November, some of his former detractors have transformed themselves -- from some of his strongest critics into fervent allies.

Over the past few years, many have done a complete 180 and have embraced the former president after lambasting him in the past.

Trump is expected to soon share who he has selected as his running mate. His senior adviser Jason Miller said Monday that Trump could announce his choice "any time this week" as the Republican National Convention approaches on July 15.

Ohio Sen. J.D. Vance -- who rose to prominence through his book "Hillbilly Elegy" -- has been the most critical of Trump in the past. Now Vance is among those being considered as Trump's running mate.

When Vance first came into the spotlight through his book, he expressed his dislike of the former president's rhetoric and style during his first presidential run.

In August 2016, he told ABC News that he didn't see Trump "offering many solutions."

In a separate interview with Charlie Rose that same year, Vance said he was a "never Trump guy" and never liked him.

In 2021, CNN reported on now-deleted tweets and comments from Vance in 2016 attacking the former president and calling him "reprehensible."

In a 2016 interview with NPR, Vance even suggested that he might vote for former Secretary of State Hillary Clinton if he believed that Trump had a chance of winning the election.

"My current plan is to vote either third party or, as I joked to my wife, I might write in my dog because that's about as good as it seems," Vance told NPR in August 2016. "But, you know, I think there's a chance, if I feel like Trump has a really good chance of winning, that I might have to hold my nose and vote for Hillary Clinton. But at the end of the day, I just feel like she is so culturally disconnected from the people that I grew up around that it would be very, very hard for me to cast my ballot for her."

However, in 2021, following the launch of his Senate campaign, Vance apologized for his past criticisms of Trump.

"I've been very open about the fact that I did say those critical things, and I regret them, and I regret being wrong about the guy," Vance said on Fox News in 2021.

Fox News anchor Bret Baier confronted Vance last month about his anti-Trump comments.

"Look, I was wrong about Donald Trump. I didn't think he was going to be a good president, Bret," 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."

"... When you are wrong about something -- you should change your mind and be honest with people about that fact," Vance continued.

Things between the two have mended, though, with Vance scoring Trump's endorsement in the Ohio Senate GOP primary and now possibly being a top contender to serve as Trump's running mate.

Florida Sen. Marco Rubio, another person among Trump's possible running mates, has been a vocal critic of Trump in the past.

Rubio attacked the former president fiercely during the latter part of 2016, the GOP primary, when the two were competitors against each other. Things turned vulgar at one point.

Trump called Rubio "little Marco," and Rubio called Trump a "con artist" and said that he has "small hands."

"He's always calling me little Marco … he's taller than me, he's like 6'2", which is why I don't understand why his hands are the size of someone who is 5'2" and you know what they say about men with small hands," Rubio said during a campaign event in 2016.

However, Rubio would later drop out of the GOP primary after Trump beat him in his home state of Florida. In his concession speech, Rubio made a veiled swipe at Trump.

"After tonight, it is clear that while we are on the right side, this year, we will not be on the winning side."

But the relationship between the two would eventually get better as Trump relied on the Florida senator during his presidency, turning to him on policies relating to Latin America.

Asked about his 2016 remarks about Trump during an appearance on ABC News' "This Week" in March, Rubio explained: "It was a campaign."

North Dakota Gov. Doug Burgum, another one of Trump's potential vice presidential picks, has also criticized the former president, but not nearly to the same degree as Rubio or Vance.

One of his harshest critiques about the former president came during an interview with NBC News in July 2023, where Burgum, a retired businessman, was asked if he would do business with the former president. He said he would not.

"I don't think so," Burgum responded. Asked why, he said, "I just think that it's important that you're judged by the company you keep."

But following the suspension of his presidential campaign, Burgum endorsed Trump in the 2024 GOP primary and has become one of his biggest campaign surrogates.