After months of speculation, former New York City Mayor Michael Bloomberg confirmed Tuesday afternoon that he will not run for president in 2020, citing the difficulties he expected to face if he joined the large Democratic field.

In an op-ed released on the Bloomberg website, the former three-term mayor said he believes he would beat President Donald Trump in a general election but added that he was "clear-eyed about the difficulty of winning the Democratic nomination in such a crowded field."

Bloomberg also said in his op-ed that, until 2021, "our only real hope for progress lies outside of Washington."

"I've come to realize that I’m less interested in talking than doing. And I have concluded that, for now, the best way for me to help our country is by rolling up my sleeves and continuing to get work done," Bloomberg said in the op-ed.

The 77-year-old Bloomberg was elected to three terms as New York City mayor — twice as a Republican in 2001 and 2005, and once as an independent on the Republican line in 2009.

He switched his political affiliation from the Democratic Party to the Republican Party ahead of his first successful run for mayor in 2001. He became an independent in 2007, two years before he won a third term as mayor.

MONTHS OF SPECULATION

First, there was the 2008 cycle, when then-Mayor Bloomberg left the Republican Party, fueling speculation he would run for president as an independent. He ultimately took a pass.

"I've thought long and hard, it's been very flattering," he said at the time.

A similar sequence played out in 2012 and 2016, when Bloomberg determined he had no path to victory and could in fact throw the race to Trump.

But the billionaire has been fueling speculation of a 2020 run for months. Last October, he seemingly decided his best shot at winning was as a Democrat, re-registering with the party, arguing Democrats "provide the checks and balance our nation so badly needs." He also poured $110 million into U.S. House of Representatives races on behalf of Democrats.

Bloomberg was also barnstorming the country, including a December trip to Iowa, home to the first-in-the-nation nominating contest. Ostensibly, he was there to promote a new climate change documentary he helped fund. But he also attended events focused on renewable energy that had the feel of campaign stops, and had private meetings with top Iowa Democrats.

In interviews, he seemed to be rehearsing his pitch to voters: "I have a lot of experience which would be useful if I was president of the United States. That doesn't mean I'm going to run."

But there was no secret he was seriously considering it. Bloomberg, who premiered the documentary in Manhattan, was even thinking ahead to what might become of his business, Bloomberg L.P., telling an interviewer he'd likely sell or put the business into a blind trust if he won the White House.

Bloomberg said he would decide by February, but his team had been looking at possible campaign office spaces in Manhattan, according to a source. The source told NY1 last week that Bloomberg's advisers were considering the former New York Times Building on West 43rd Street and 7 World Trade Center as possible options.

Ultimately, Bloomberg, as he has done in the past, explored a run but ended up not following through.