Michael Bloomberg Will Not Run for President in 2020

So, too, might the scrutiny facing the wider field of Democratic candidates on the issue of criminal justice policy. Other contenders, including Mr. Biden and Senator Kamala Harris of California, have been pushed onto the defensive for having pursued traditional tough-on-crime policies in the past. As mayor of New York, Mr. Bloomberg supported stop-and-frisk policing, which was found to target black and Hispanic people disproportionately.

In a September interview, Mr. Bloomberg expressed no regret about employing aggressive policing tactics as mayor, and questioned whether many of the allegations arising as a result of #MeToo deserved to be believed. He described his emerging identity as a Democrat as something of a default choice, citing his support for abortion rights.

“It’s impossible to conceive that I could run as a Republican — things like choice, so many of the issues, I’m just way away from where the Republican Party is today,” Mr. Bloomberg said.

Where Mr. Bloomberg has aligned most cleanly with Democrats has been his contempt for Mr. Trump, whom he has described routinely as divisive and incompetent. After endorsing Hillary Clinton for president in 2016, Mr. Bloomberg threw his political clout wholly behind Democrats in the 2018 midterm elections, spending about $112 million to lift the party and dedicating most of that sum to seizing control of the House.

Mr. Bloomberg has been welcomed into the top ranks of the Democratic Party with open arms. On Tuesday, both Speaker Nancy Pelosi and Senator Chuck Schumer of New York, the Democratic minority leader, praised Mr. Bloomberg in glowing language.

Mr. Schumer said he was “a great mayor and would have been a strong candidate,” while Ms. Pelosi said his candidacy would have been an “important addition to the discussion about how we go forward as a country.”

In a boon to Democrats, Mr. Bloomberg is expected to keep intact the political operation he assembled for a presidential race, which includes a number of former top advisers to President Barack Obama and Hillary Clinton, and to deploy it instead on a project to help build Democratic infrastructure for the party’s eventual nominee.