update: See: Brian Schwartz.  "Mike Bloomberg keeps talking to allies about running for president as Joe Biden struggles against Elizabeth Warren."  CNBC, Oct. 14, 2019.


https://www.bloomberg.com/opinion/articles/2019-03-05/our-highest-office-my-deepest-obligation

March 5, 2019 - Michael Bloomberg Will Not Run

Former Mayor Mike Bloomberg announced he would not run in a March 5, 2019 Op-Ed on Bloomberg Opinion titled "Our Highest Office, My Deepest Obligation."  He stated, "I’m not running for president, but I am launching a new campaign: Beyond Carbon."  Bloomberg wrote:

"I know what it takes to run a winning campaign, and every day when I read the news, I grow more frustrated by the incompetence in the Oval Office. I know we can do better as a country. And I believe I would defeat Donald Trump in a general election. But I am clear-eyed about the difficulty of winning the Democratic nomination in such a crowded field."

Bloomberg cited his work on "initiatives that are rallying citizens and leaders of cities, states, businesses, and nonprofit organizations to take action on their own" and said a presidential campaign would limit his ability to continue those activities.  He described the choice as:

"Should I devote the next two years to talking about my ideas and record, knowing that I might never win the Democratic nomination? Or should I spend the next two years doubling down on the work that I am already leading and funding, and that I know can produce real and beneficial results for the country, right now?"


Background: In 2016 Bloomberg considered an independent run for president, but he ruled it out on March (+).  He addressed the 2016 Democratic National Convention in Philadelphia on the evening of July 27 explaining his view that "it is imperative that we elect Hillary Clinton as the next president of the United States."  He sharplly criticized Trump, declaring, "I'm a New Yorker and I know a con when I see one (>)."  Bloomberg firmly aligned with the Democratic Party for the 2018 midterms.  He provided a total of $110 million to support Democrats in the 2018 cycle, much through his Independence USA PAC, and emphasized taking back the U.S. House (1, 2). 

Additionally, on Oct. 10, 2018 he announced he was re-registering as a Democrat.  In an Instagram post he wrote, "At key points in U.S. history, one of the two parties has served as a bulwark against those who threaten our Constitution. Two years ago at the Democratic Convention, I warned of those threats. Today, I have re-registered as a Democrat – I had been a member for most of my life – because we need Democrats to provide the checks and balance our nation so badly needs."

However, Bloomberg didn't fit the picture of a traditional Democrat.  He was described as a "pragmatic centrist," and if he ran he would likely have faced difficully attracting support of the progressive activists who are a critical part of the party.  Bloomberg's age might have been an issue as well;
he will be 78 years 11.2 mos on Inauguration Day 2021. 

Still, Bloomberg has been a leader on several issues important to Democrats, specifically gun violence and climate change
(+).  Bloomberg was a co-founder of Mayors Against Illegal Guns in 2006 and has provided much of the backing for Everytown for Gun Safety.  He teamed with former Sierra Club chairman Carl Pope to author Climate of Hope (St. Martin's Press, April 2017).  In July 2017 he teamed up with Gov. Jerry Brown (D-CA) to launch America’s Pledge on climate change "a new initiative to compile and quantify the actions of states, cities and businesses in the United States to drive down their greenhouse gas emissions consistent with the goals of the Paris Agreement."   More recently the Bloomberg Philanthropies documentary Paris to Pittsburgh premiered on Dec. 12, 2018.  

Meanwhile Bloomberg did lay the groundwork for a possible presidential campaign.  In Jan. 2019, he released a revised and updated edition of his biography, Bloomberg on Bloomberg (Wiley & Sons).  Longtime aide Kevin Sheekey led Bloomberg's political efforts.  In Oct. 2018 he spoke to Moms Demand Action in Nashua, NH.  On Jan. 28-29 he visited New Hampshire again, having a dinner with local political leaders, meeting with entrepreneurs from Manchester and speaking at Saint Anselm College (>).  As recently as March 1, 2019 CNBC reported, "Bloomberg aides interview potential staffers in New Hampshire and Iowa."


See.
Brian Schwartz.  "Bloomberg aides interview potential staffers in New Hampshire and Iowa as the former mayor considers a 2020 run."  CNBC, March 1, 2019.

Speech at U.S. Conference of Mayors 2019 Winter Meeting, Jan. 25, 2019.