Even from the beginning, Mitch McConnell and Donald Trump had a complicated relationship.
In 1989, McConnell was running for reelection to the Senate. As he once told a Senate committee, the reason he and other lawmakers spent much of their time fundraising was because "we like to win."
And that fall, he received a $1,000 campaign check (the legal maximum at the time) from one prolific political donor: then-real estate developer and author of the bestselling The Art Of The Deal Donald J. Trump.
But in 1990, Trump's financial fortunes — and the headlines he generated — changed.
Many of his casinos were underperforming, some on the verge of bankruptcy. And Forbes magazine dropped Trump from its annual list of the 400 wealthiest people, saying that his fortune was "within hailing distance of zero."
According to recent reporting by the New York Times, Trump lost a combined $517.6 million between 1990 and 1991.
McConnell's opponent in his Senate race, Democrat Harvey Sloane, started criticizing the freshman senator for getting out-of-state campaign contributions like the check from Trump.
"Kentucky needs a relatively obscure senator as much as Donald Trump needs another casino," Sloane said, according to an Associated Press story at the time.
Facing attacks from his opponent and bad headlines, McConnell tried to distance himself from the donation.
McConnell said he'd never met Trump personally, and then he actually decided to return the $1,000 campaign check to Trump.
"While I thank you for your contribution, I have noticed several stories in the last few weeks about your financial difficulties," McConnell wrote in a letter to Trump, which was also provided to the press.
"Although I am certain you will recover," McConnell went on, "I have decided to return your contribution of $1,000, because it appears you may need the money more than I do right now."
The returned check did not make much of a dent in Trump's debts. The Trump Taj Mahal actually filed for Chapter 11 bankruptcy protection the next year.
The White House did not respond to NPR's request for comment.
It was an uncomfortable beginning to what would go on to become, decades later, one of the most important, if complicated, relationships in politics.
"Not a happy choice"
There are few Republicans more different from each other than McConnell and Trump.
"I couldn't write the story to have two people who were more unlike than those two," says Janet Mullins Grissom, who served as McConnell's campaign manager and chief of staff in the 1980s.
Despite their differences, these two politicians have gone from publicly feuding to largely embracing each other's agendas.
In the summer of 2016, McConnell was on tour promoting his recently published memoir, The Long Game. But it was the middle of the presidential election, and people wanted to know how McConnell felt about Trump, then the presumptive Republican nominee.
By that time, Trump had said Republican Sen. John McCain of Arizona was not a war hero, mocked a reporter with a disability, and proposed banning all Muslims from entering the United States. Trump had also said a federal judge whose parents emigrated from Mexico could not be impartial in a lawsuit against Trump University, because Trump was promising to build a wall on the southern border.
"Mitch was not thrilled when Trump was last man standing and got the nomination," says Grissom. "He didn't keep it a secret."
In an interview with PBS NewsHour, McConnell condemned Trump's comments about the judge, calling them "outrageous and inappropriate."
"[There are] plenty of things he ought to be talking about, rather than taking shots at Americans because of their ethnicity," McConnell said.
"The choice for many Americans," McConnell said of the election between Trump and Hillary Clinton, "is not a happy choice."
"It's pretty obvious [Trump] doesn't know a lot about the issues," McConnell told Bloomberg's "Masters In Politics" podcast.
The show's host, Betsy Fischer Martin, asked McConnell if there was a line Trump could cross, at which point McConnell would withdraw his support.
"I'm not going to speculate about what he might say or what I might do," McConnell said. "But I think it's pretty clear, I've been very clear publicly, about how I think he ought to change directions. And I hope that's what we're going to see."
Trump's election in 2016 caught many by surprise, including McConnell.
"They didn't have the kind of relationship that a lot of Republican leaders would have with an incoming Republican president," says political strategist Josh Holmes, a former chief of staff to McConnell. "So you had to start from scratch in some ways."
But even after winning the presidency, Trump's rhetoric — particularly toward his personal and political opponents — largely did not change.
And so McConnell time and again has been asked to answer a version of that same question: What would it take for the Senate majority leader to break from the president?
Avoiding a "public war" with Trump
For some, a critical line came in August 2017, after the deadly Unite The Right rally in Charlottesville, Va. In a news conference, Trump said there were "very fine people" on both sides of the white supremacist rally.
Many rushed to condemn the president's remarks. But McConnell's response was more tempered.
In a sign of just how complicated his relationship with Trump had become, McConnell's wife, Secretary of Transportation Elaine Chao, was standing behind the president during his remarks.
"There are no good neo-Nazis, and those who espouse their views are not supporters of American ideals and freedoms," McConnell's office said in a written statement at the time. "We all have a responsibility to stand against hate and violence, wherever it raises its evil head."
The statement does not mention Trump's name or specifically reference the president's controversial remarks.
NPR specifically asked McConnell why he did not mention the president in his statement after the events in Charlottesville.
In an email, he responded, "Messages of hate and bigotry are not welcome in Kentucky and should not be welcome anywhere in America."
Republican strategist Antonia Ferrier, a former communications adviser to McConnell, says she believes McConnell is more effective keeping much of his criticism private.
"Getting into a public war with Donald Trump is usually not a good thing from anyone's perspective," says Ferrier, "especially if you're trying to keep an even-keeled ship moving forward."
"I think one of the most important things McConnell has done is normalize Donald Trump," says Al Cross, a Kentucky-based journalist who has covered McConnell for decades. "He treats him as an entirely legitimate president."
Based on his decades of experience covering and interviewing McConnell, Cross says he believes McConnell privately "abhors" Trump's behavior. And yet McConnell is careful to avoid publicly breaking with the president.
Journalist Keith Runyon, a former editorial page editor of the Louisville Courier-Journal who has known McConnell since the 1970s, says he wishes McConnell would use his leadership role to publicly denounce Trump's rhetoric.
"If he were to do that, he would earn a chapter in Profiles in Courage," says Runyon, referring to John F. Kennedy's book on political acts of bravery.
"I think Mitch has it in him," Runyon says. "I hope he does. But I don't know."
"I'm not a mirror image of the president."
In an interview with NPR's Embedded podcast, McConnell says there's a simple explanation for his public support for the president — and his general reluctance to publicly break with him.
"What [Democrats] would hope is we would join them and torpedo him and do nothing," McConnell says. "I mean that's not my idea of what our responsibility is."
"There are many things that he's willing to go along with that are consistent with what members of my party have thought for years ought to be done," McConnell says, citing tax cuts and regulatory rollbacks, for example.
McConnell has also worked closely with the Trump administration to confirm conservative judges to the federal courts. Together, they have already confirmed more than 40 judges to the U.S. Court of Appeals, meaning more than 20% of all circuit court judges were nominated by Trump.
McConnell notes that he has disagreed with Trump about trade and tariffs, as well as support for NATO.
"I'm not a mirror image of the president. But I'm glad he got elected," McConnell says. "It doesn't mean you're devoid of principle. But you have to make compromises and you have to try to advance the ball or you make no difference."
The government shutdown and an "uncharacteristic" move
Cross, who is also the director of the Institute for Rural Journalism and Community Issues at the University of Kentucky, says that pattern has held even during one of the most consequential moments of Trump's presidency, the partial government shutdown in the winter of 2018-2019.
McConnell has long been on the record opposing government shutdowns and executive overreach. When the government shut down under President Barack Obama, he called shutdowns a "losing strategy." When Obama pushed executive actions to prevent deportations, McConnell said, "The action he's proposed would ignore the law, would reject the voice of the voters."
But McConnell's opposition to shutdowns did not prevent this outcome: The partial government shutdown ultimately became the longest in American history.
And McConnell ultimately said he supported Trump's declaration of a national emergency to divert funds to construct a border wall, even without the approval of Congress.
Given McConnell's stated record on government shutdowns and executive actions, Cross calls it, "one of the most uncharacteristic things he has ever done."
In a statement, McConnell's office told NPR, "There [was and continues to be] a clear border security and humanitarian crisis on our southern border."
"Sometimes you have to make sacrifices or compromises to do what you think is for the greater good," says Ferrier.
Navigating Kentucky politics
Cross says McConnell's embrace of Trump has another motivation: getting reelected in Kentucky in 2020. According to polling from Morning Consult, McConnell is the least popular senator in the country.
"And because Donald Trump is very popular in Kentucky," Cross says, "that means not getting much distance between himself and Donald Trump."
Democrat Amy McGrath, a retired Marine Corps fighter pilot, announced this week that she will challenge McConnell in 2020.
Former McConnell adviser Holmes told Politico that anyone who entered the race would face "a symphony of absolute destruction" from McConnell and his allies, and the McConnell campaign has already released a video attacking McGrath. The campaign argues that she poses a threat to "passing President Trump's agenda, confirming conservative judges, even our Republican Senate Majority itself."
McConnell is also counting on Trump's support in the election.
On Tuesday, Trump tweeted his support for McConnell's 2020 run, saying, "We need Mitch in the Senate to Keep America Great!!"
At a late 2018 rally in Richmond, Ky., McConnell and Trump shared a stage and paid each other many compliments.
Trump said McConnell was "one of the most powerful men in the world," calling him "rock-ribbed" and "Kentucky Tough."
"Aren't we proud of President Trump?" McConnell asked the thousands in attendance.
The event was a remarkable turnaround from 2016, when McConnell was openly critical of the president, and from 1990, when McConnell could mock Trump's financial misfortune.
McConnell's campaign is now selling T-shirts for his reelection with the slogan "Kentucky Tough."