Starbucks' former CEO Howard Schultz has been battling Trump for years. Now, he is considering running for president.

In 2016, Starbucks supporters attempted to take matters into their own hands, asking the company to terminate its lease. Hundreds of people pledged to buy more than $40,000 in Starbucks gift cards if the company terminated its lease.

"The money Starbucks gives Trump every month is used to fund the bigotry and racism that he broadcasts across the country," the pledge read. "Macy's, NBC-Universal, ESPN, Apple, and NASCAR have all cut ties with Trump, but Starbucks continues to hold out, forcing us to unwillingly fund Donald Trump's hate with every latte bought."

Read more: Starbucks customers have pledged to buy $40,000 in gift cards if the coffee giant ditches Donald Trump

In September 2016, Schultz endorsed Clinton, the first time he publicly came out in support of a presidential candidate.

"I think it's obvious that Hillary Clinton needs to be the next president," Schultz told CNN's Poppy Harlow. "On the other side, we've seen such vitriolic display of bigotry and hate and divisiveness, and that is not the leadership we need for the future of the country."

Read more: Starbucks CEO endorses Hillary Clinton

Schultz sent a solemn note to his company's more than 120,000 US employees on the morning after Trump's victory in the presidential election.

"Last night, like so many of you, I watched the election returns with family and friends," the note began. "And like so many of our fellow Americans — both Democrats and Republicans — I am stunned."

The CEO went on to encourage the chain's workers to move "onward together."

Read more: Starbucks CEO Howard Schultz 'stunned' by Trump's election

While neither Schultz nor Trump were directly involved, the Trump cup incident revealed how Starbucks has become a political touchstone in the Trump era.

"We have a culture war to win," Baked Alaska said in a Periscope video, encouraging people to tell Starbucks baristas that they were named "Trump."

"If someone is getting so triggered, they can't write Trump on a coffee cup at Starbucks and they're crying liberal tears and they're calling the cops, that's insane," the Trump supporter said in a video, in which he also complained about alt-right Twitter account suspensions and accused liberals of making white people and men feel guilty.

According to Baked Alaska, the purpose of asking baristas to write "Trump" on cups was to "trigger SJW" employees (SJW is an abbreviation for social justice warrior, a derogatory term for feminists and progressives). He says that asking to write Trump on the cups was a way to normalize Trump and the alt-right.

Read more: 'We have a culture war to win': Trump supporters are having baristas write his name on their Starbucks cups

In January 2017, Starbucks announced it planned to hire 10,000 refugees worldwide in the next five years.

"We are living in an unprecedented time, one in which we are witness to the conscience of our country, and the promise of the American Dream, being called into question," Schultz wrote in a letter to Starbucks employees about the plan.

Trump supporters responded negatively, with some saying they were angry that Starbucks was hiring refugees instead of veterans. Starbucks, however, does have a program in place to support veterans and their families, hiring thousands of military veterans and spouses.

Read more: People are boycotting Starbucks after CEO announces plan to hire thousands of refugees

"The world is screwed up. People are unsettled," Schultz said during a meeting with the company's support staff in Seattle in February 2017. "There is a tremendous amount of pressure and anxiety in America."

"We have a president that is creating episodic chaos every single day and that is no doubt affecting consumer behavior," Schultz said in a video of the meeting obtained by Business Insider.

Read more: Leaked video shows Howard Schultz telling Starbucks workers of Trump creating 'chaos' with economic impact

"So many people in America are living paycheck to paycheck. Corporate America does not need a corporate tax cut from 35 to 20%," Schultz told Andrew Ross Sorkin at the New York Times' DealBook conference. "If you're going to do that, it has to be more balanced, it has to be more common sense."

While Schultz did not specifically address Trump beyond the GOP tax plan, the then-Starbucks chairman also said he believed that the position of president should be one of "civility, of respect."

"Young people in America … have been imprinted with an America that is not the same America I grew up with," Schultz said. "We are being imprinted with a level of dysfunction, polarization, vitriolic behavior that I think is not in keeping with the spirit of the country and the promise of the country."

Read more: Starbucks' chairman slams GOP tax plan

On Sunday, Schultz said he was "seriously considering running for president as a centrist independent."

In an interview with "60 Minutes," Schultz repeatedly criticized Trump's lack of qualifications and cited shortcomings of both Democrats and Republicans as a reason he would run as an independent.

"Not only the fact that this president is not qualified to be the president, but the fact that both parties are consistently not doing what's necessary on behalf of the American people and are engaged every single day in revenge politics," Schultz said.

Read more: Former Starbucks CEO Howard Schultz announces he's 'seriously considering running for president' as an independent

"Howard Schultz doesn't have the 'guts' to run for President!" Trump tweeted. "Watched him on @60Minutes last night and I agree with him that he is not the 'smartest person.'"

He added: "Besides, America already has that! I only hope that Starbucks is still paying me their rent in Trump Tower!"

On Sunday, Schultz said in his "60 Minutes" interview: "I've become bored with President Trump and his tweets."

Read more: Trump slams Howard Schultz after the ex-Starbucks CEO announces he's considering running for president