Photo: The Canadian Press

Former New York City Mayor Michael Bloomberg 

Michael Bloomberg, the billionaire former mayor of New York City, is opening the door to a 2020 Democratic presidential campaign, warning that the current field of candidates is ill equipped to defeat President Donald Trump.

Bloomberg, who initially ruled out a 2020 run, has not made a final decision on whether to jump into the race. If he were to launch a campaign, it could dramatically reshape the Democratic contest less than three months before primary voting begins.

The 77-year-old has spent the past few weeks talking with prominent Democrats about the state of the 2020 field, expressing concerns about the steadiness of former Vice-President Joe Biden's campaign and the rise of liberal Massachusetts Sen. Elizabeth Warren, according to people with knowledge of those discussions. In recent days, he took steps to keep his options open, including moving to get on the primary ballot in Alabama ahead of the state's Friday filing deadline.

In a statement on Thursday, Bloomberg adviser Howard Wolfson said the former mayor believes Trump "represents an unprecedented threat to our nation" and must be defeated.

"But Mike is increasingly concerned that the current field of candidates is not well positioned to do that," Wolfson said.

Bloomberg's moves come as the Democratic race enters a crucial phase. Biden's front-runner status has been vigorously challenged by Warren and Vermont Sen. Bernie Sanders, who are flush with cash from small-dollar donors. But both are viewed by some Democrats as too liberal to win in a general election faceoff with Trump.

Despite a historically large field, some Democrats anxious about defeating Trump have been looking for other options. Former Attorney General Eric Holder and former Massachusetts Gov. Deval Patrick have quietly had conversations with supporters urging them to consider a run, but neither appears likely to get in the race.

Bloomberg, a Republican-turned-independent who registered as a Democrat last year, has flirted with a presidential run before but ultimately backed down, including in 2016. He endorsed Hillary Clinton in that race and, in a speech at the Democratic Party convention, pummeled Trump as a con who has oversold his business successes.

Bloomberg plunged his efforts — and his money — into gun control advocacy and climate change initiatives. He again looked seriously at a presidential bid earlier this year, travelling to early voting states and conducting extensive polling, but decided not to run in part because of Biden's perceived strength.

Biden did not address Bloomberg's potential candidacy at a fundraiser Thursday night in Boston.

With immense personal wealth, Bloomberg could quickly build out a robust campaign operation across the country. Still, his advisers acknowledge that his late entry to the race could make competing in states like Iowa and New Hampshire, which have been blanketed by candidates for nearly a year, difficult. Instead, they previewed a strategy that would focus more heavily on the March 3 "Super Tuesday" contests, including in delegate-rich California.