In an interview with the New York Times, four months before Donald Trump declared himself a candidate for president, Stephen K. Bannon indicated that he was not prepared to take the celebrity businessman seriously.

“There are a lot of reasons for running for president,” Bannon said, observing the promotional efforts of Trump, Sarah Palin and Newt Gingrich at the Conservative Political Action Conference in February 2015. “And getting to 1600 Pennsylvania Avenue often isn't one of them.”

With Trump and Bannon now at a low point in their relationship — “he lost his mind,” the president said of his former chief strategist Wednesday — it is worth remembering that the dynamic between the two men has always been complicated. Yes, Bannon's Breitbart News outfit boosted Trump's candidacy; yes, Trump made Bannon his campaign chief executive. But their union hit rough patches before Wednesday's epic falling-out.

According to a forthcoming book by journalist Michael Wolff, in which Bannon is quoted extensively, Trump only put Bannon in charge of his campaign at the urging of major donors Robert and Rebekah Mercer. Here's an excerpt:

. . . when the Mercers presented their plan to take over the campaign and install their lieutenants, Steve Bannon and Kellyanne Conway, Trump didn’t resist. He only expressed vast incomprehension about why anyone would want to do that. “This thing,” he told the Mercers, “is so f---ed up.”

As Bannon's profile rose, Trump reportedly grew resentful. A February 2017 Time magazine cover that dubbed Bannon “the great manipulator” continued to bother the president two months later, according to the New York Times.

After one angry eruption, in March, Trump left Bannon and other senior aides in Washington when he traveled to Mar-a-Lago for the weekend.

In April, as clashes between Bannon and Jared Kushner spilled into the open, Trump cut down Bannon in an interview with the New York Post.

“I like Steve, but you have to remember he was not involved in my campaign until very late,” the president said. “I had already beaten all the senators and all the governors, and I didn’t know Steve.”

Trump made a similar point when he disowned Bannon on Wednesday, saying, “Steve was a staffer who worked for me after I had already won the nomination by defeating 17 candidates.”

Bannon hung on to his job until August, but, when he left and immediately returned to Breitbart News, he began to vent criticisms of the president. Speaking to the Weekly Standard on the day of his ouster, Bannon declared that “the Trump presidency that we fought for, and won, is over.”

A few days later, when Trump unveiled a plan to send more U.S. troops to Afghanistan, Breitbart's coverage was overwhelmingly negative.

Bannon split from Trump in September's GOP runoff between Senate candidates Luther Strange and Roy Moore in Alabama. Bannon went so far as to suggest that he understood Trumpism better than Trump himself, telling Sean Hannity that the president had made a mistake by backing Strange and that Moore would be better for Trump's agenda, whether Trump realized it or not.

Two weeks ago, the Trump and Bannon camps exchanged fire in a Vanity Fair article by Gabriel Sherman that was most notable for raising the prospect of a Bannon presidential bid in 2020. Here's an excerpt:

In October, Bannon called an adviser and said he would consider running for president if Trump doesn’t run for reelection in 2020. Which Bannon has told people is a realistic possibility. In private conversations since leaving the White House, Bannon said Trump only has a 30 percent chance of serving out his term, whether he’s impeached or removed by the Cabinet invoking the 25th amendment. That prospect seemed to become more likely in early December when special counsel Robert S. Mueller III secured a plea deal from former national security adviser Michael Flynn. Bannon has also remarked on the toll the office has taken on Trump, telling advisers his former boss has “lost a step.” “He’s like an 11-year-old child,” Bannon joked to a friend in November.

An unnamed White House official countered by telling Sherman that “the few conversations Steve and the president have had since he was fired this summer have primarily been opportunities for Steve to beg for his job back.”

Trump's latest statement on Bannon represented a dramatic escalation of tensions, to be sure. But it did not come out of the blue.