Senator Lindsey Graham's tireless work ethic never wavered, even in the days leading up to his sudden death, RadarOnline.com can reveal.

In an emotional interview with the Daily Mail, his longtime communications director, Kevin Bishop, reflected on the late lawmaker's relentless schedule, unlikely friendship with Donald Trump and the final promise he never got to keep.

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Kevin Bishop recalled Lindsey Graham's relentless work ethic after nearly three decades together.

Bishop, who worked alongside Graham for more than 27 years, said the South Carolina senator devoted nearly every waking moment to his job.

Their daily routine included a phone call after 9 a.m. almost every day of the year, except Christmas, as Graham caught up on the latest political developments.

"He was not a morning guy at all," Bishop joked, recalling how he would prepare the senator's daily briefing before their conversations.

According to Bishop, Graham viewed every moment as an opportunity to serve, saying the senator believed "God gave you so much time on this earth" and had no intention of wasting it.

"He never took a day off," Bishop said. "Even when he was on the golf course, he was working."

Many of Graham's staff remained with him for decades, with Bishop saying employees often joked that anyone who had been there for only 10 years was still considered "new."

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Kevin Bishop revealed how a few rounds of golf helped forge Lindsey Graham's close friendship with Donald Trump.

While Graham initially clashed with Trump during the president's first campaign and early days in office, Bishop said mutual friends encouraged the two Republicans to spend time together.

A few rounds of golf quickly transformed the relationship into one of Washington's closest political alliances.

"Their love language was golf," Bishop said.

The longtime aide explained that Graham's humor and willingness to speak candidly helped cement the friendship, adding that the senator could have "been a stand-up comedian."

Although many Democrats and "Never Trump" Republicans criticized Graham for becoming one of Trump's strongest allies, Bishop insisted the senator never held personal grudges against those who disagreed with him.

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The longtime aide said Lindsey Graham's famous 2018 Brett Kavanaugh speech came after he arrived at work "madder than a hornet."

Despite Graham's reputation for keeping his emotions in check, Bishop recalled one day when the senator arrived at work "madder than a hornet."

The outburst came before the explosive 2018 Senate Judiciary Committee hearing involving then-Supreme Court nominee Brett Kavanaugh.

Bishop said staff members worried Graham might lose his temper on live television, but instead he delivered what became one of the defining speeches of his career, blasting Democrats for trying to "destroy this guy's life" and calling the proceedings "the most unethical sham since I've been in politics."

Lindsey Graham's final exchange with Kevin Bishop came while the senator was traveling in Ukraine.

Bishop said his final exchange with Graham came on the senator's birthday, July 9, while he was on an overseas trip to Ukraine.

Rather than calling, Bishop sent a text, knowing Graham typically avoided phone conversations while traveling abroad because he believed foreign adversaries could be monitoring communications.

Graham responded that they would reconnect after he returned to the United States. For Bishop, that message became their final conversation.