President Donald Trump and Senate Majority Leader Mitch McConnell Evan Vucci/AP Images

Senate Majority Leader Mitch McConnell once reportedly returned $1,000 to then-real-estate developer Donald Trump in 1989, telling the future president at the time that he needed the money more than he did.

During McConnell's Senate reelection campaign that fall, the Kentucky Republican received a $1,000 campaign check from Trump, the highest amount allowed under campaign law, NPR reported.

But Trump ran into financial headwinds and started generating negative headlines less than a year later.

McConnell then released a letter to the press announcing he was returning the donation to distance himself from Trump.

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Senate Majority Leader Mitch McConnell once reportedly returned a $1,000 campaign donation to then-real-estate developer Donald Trump, telling the future president at the time that he needed the money more than he did.

During McConnell's Senate reelection campaign in 1989, the Kentucky Republican received a $1,000 campaign donation from Trump, the highest amount allowed under campaign law, NPR reported. Trump had crafted a reputation as a business titan and successful author with the bestselling book "The Art of the Deal." He was also throwing his weight into politics, donating almost $50,000 to mostly Republican candidates in 1989.

Read more: If a Democrat beats Trump in 2020, they might still have to face the toughest obstacle in politics — Mitch McConnell

But Trump ran into financial headwinds and started generating negative headlines less than a year later. His business empire was fracturing, burdened by high debt, low revenue and overexpansion, according to Wired.

Then Forbes Magazine dropped Trump from its annual list of the 400 wealthiest people, saying his fortune was "within hailing distance of zero." The New York Times recently reported 1990 and 1991 were among the worst years for Trump's finances that they examined, adding up to $517.6 million in combined losses.

McConnell's opponent, Harvey Sloane, saw an opportunity and pummeled the one-term senator for accepting out-of-state campaign contributions from figures like Trump.

Read more: Mitch McConnell was a clear political target in the first 2020 Democratic debate, but he didn't seem to mind

"Kentucky needs a relatively obscure senator as much as Donald Trump needs another casino," Sloane said, according to NPR.

McConnell then released a letter to the press announcing he was returning the donation to distance himself from Trump.

"While I thank you for your contribution, I have noticed several stories in the last few weeks about your financial difficulties," McConnell wrote.

"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 relationship between the two, however, has evolved over the years. Though McConnell was occasionally critical of Trump during the 2016 campaign, they developed an unlikely partnership in the Trump era. McConnell has been successful muscling scores of conservative federal judges through the Senate and helping pass the 2017 GOP tax law, two key tenets of Trump's campaign promises.