Former Starbucks CEO and businessman Howard Schultz announced he has ended his unofficial bid for president as an independent, months after he ducked out of the public eye after suffering a back injury.

Schultz never formally declared his candidacy, but had expressed his intention to run.

In a letter to supporters on his website, Schultz wrote that he has realized current election rules and the domination of "extreme voices" in the major political parties make it unlikely his run would succeed in overtaking President Donald Trump.

"[N]ot enough people today are willing to consider backing an independent candidate because they fear doing so might lead to re-electing a uniquely dangerous incumbent president," Schultz wrote.

He continued: "If I went forward, there is a risk that my name would appear on ballots even if a moderate Democrat wins the nomination, and that is not a risk I am willing to take."

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He also cited recent health issues as a reason for his decision. In June, he had announced he was taking a step back from engaging with his supporters for the summer due to a back injury sustained in April.

He was running on the platform of being a "centrist independent," able to appeal to moderate voters from both parties. But, he pledged not to run unless he was confident he could win.

"My belief in the need to reform our two-party system has not wavered, but I have concluded that an independent campaign for the White House is not how I can best serve our country at this time," Schultz wrote.

He says the money he was planning to invest in his run will go toward other organizations and people that "promote honesty, civility and results in our politics, and that move the country beyond two-party gridlock."

Axios, which first reported on Schultz's decision, said his "Dear Friends" letter would be sent out to supporters on Friday.

This article originally appeared on USA TODAY: Howard Schultz, ex Starbucks CEO, says he won't run for president