By Kate Sullivan, CNN

Howard Schultz said Wednesday he is taking the summer off from exploring a potential run for the presidency in order to recover after undergoing three back surgeries. A source close to the former Starbucks CEO says there have been staff reductions on his team as he steps away from the trail.

Schultz's quixotic political adventure began earlier this year when he announced that he would explore running against President Donald Trump in 2020. Despite holding pseudo-campaign events in the first few months of the year, Schultz has not announced a formal presidential run and had largely disappeared from the political scene in recent months.

On Wednesday, he chalked that up to back pain.

"While I was in Arizona, I unfortunately experienced acute back pain that required me to cut my travels short. Over the following two months, I underwent three separate back surgeries," the former Starbucks CEO, who is considering running as a "centrist independent," wrote in a letter to supporters.

"Today, I am feeling much better, and my doctors foresee a full recovery so long as I rest and rehabilitate," he wrote. "I have decided to take the summer to do just that."

Schultz wrote his "concern for our country's future remains," and that "the American people deserve so much more from our elected officials." He said he would be "back in touch" with supporters after Labor Day.

"I take this detour from the road reluctantly," he said.

A source close to Schultz said that the former executive confirmed that there have been cuts in Schultz's political staffing, which was first reported by The Huffington Post. Schultz is "realigning his team as he moves into the next phase of an exploration," the source told CNN.

The source said Schultz is not ending his presidential ambitions.

"They haven't gone away. He is still thinking about it," the source said. "He is not foreclosing the opportunity. He wants to keep the option open."

But one campaign adviser offered a much bleaker assessment of Wednesday's events.

The staffer told CNN severance packages were offered to campaign staffers, including some who had recently moved to Seattle. The announcement took many by surprise.

"It's over," the adviser told CNN, adding that the chances of Schultz still running have been all but extinguished.

Schultz's pause from the campaign trail comes after months of criticism from the left about his potential candidacy.

Several Democrats have voiced concern over a potential Schultz White House bid, with some of the party's top operatives worrying the billionaire would split the anti-Trump vote and ensure the Republican gets four more years in the White House.

Schultz, during a CNN Town Hall earlier this year, would not commit to getting out of the presidential race late in the game if his hypothetical candidacy would help Trump get elected. He said he would not run if, in the next few months, "math doesn't tally up," but he declined to say he would do the same later in the race, should he decide to run.

Schultz at the time also knocked what he called "extreme" left and right proposals on issues ranging from tax policy to climate change. Schultz provided few specific proposals of his own at the February town hall, admitting several times that he didn't know how to fix the country's problems and suggesting at other times that he would address them by breaking up government bureaucracy.