McConnell endorses Trump in 2024 race despite railing against him after Jan. 6

McConnell issued a statement just after Nikki Haley bowed out of the race.

"It should come as no surprise that as nominee, he will have my support," McConnell added. "During his Presidency, we worked together to accomplish great things for the American people including tax reform that supercharged our economy and a generational change of our federal judiciary - most importantly, the Supreme Court."

"I look forward to the opportunity of switching from playing defense against the terrible policies the Biden administration has pursued to a sustained offense geared towards making a real difference in improving the lives of the American people."

Asked about his endorsement of Trump during his weekly news conference Wednesday, McConnell referred to a prior statement from February 2021, in which he said he'd back Trump if he became the Republican nominee again.

"I don't have anything to add to what I just said. I said in February of 2021, shortly after the attack on the Capitol, that I would support President Trump if he were the nominee of our party, and he obviously is going to be the nominee of our party."

Advisers close to Trump and McConnell had been in talks for six weeks over an endorsement, sources confirmed to ABC News, as well as an overall strategy to unite Republicans to win back the Senate in November.

The conversations between the two campaigns went through a single channel: Chris LaCivita, a top campaign adviser to Trump and Josh Holmes, a longtime political strategist to McConnell.

McConnell's backing comes even though he has a strained relationship with the former president. The two men have not spoken since December 2020.

McConnell was highly critical of Trump after the Jan. 6 attack on the U.S. Capitol, calling him morally and practically responsible for the violent riot. He suggested Trump should be prosecuted for his role in what transpired.

Meanwhile, Trump has viciously attacked McConnell over the years, calling his wife, former Trump Transportation Secretary Elaine Chao, "Coco Chao" and suggesting she was a Chinese agent.

Now that he is the last major GOP candidate standing, Trump is calling for unity as his campaign enters the general election phase.

"We have a great Republican Party with tremendous talent," he said Tuesday night. "And we want to have unity and we're going to have unity and it's going to happen very quickly."

McConnell, the longest serving Senate leader in history, recently announced he will step down from the position but made it clear he will do everything he can to win back the Senate.

"I still have enough gas in the tank to thoroughly disappoint my critics, and I intend to do so with all the enthusiasm which they have become accustomed," McConnell said.