Analysts had suggested his bid for the Democratic nomination would struggle, particularly if former vice president Joe Biden joins the race.
In December Mr Bloomberg flew to Iowa in a visit that was widely considered to be testing the waters for a presidential run.
He previously considered running in 2016 — as an independent — but concluded he could improve Mr Trump’s chances of victory by attracting voters who would otherwise support Hillary Clinton.
In Tuesday’s editorial, Mr Bloomberg urged Democrats to nominate a candidate “who will be in the strongest position to defeat Donald Trump and bring our country back together.
“We cannot allow the primary process to drag the party to an extreme that would diminish our chances in the general election and translate into ‘Four More Years.’”
