In a packed Democratic field, and amid a tight race between former Vice-President Joe Biden and Massachusetts Sen. Elizabeth Warren, there are new reports that former New York Mayor Michael Bloomberg may consider a bid for the nomination.

Bloomberg, who has long been a staunch critic of President Trump, is believed to be considering joining the Democratic field as a moderate alternative to Sens. Warren and Bernie Sanders, who are seen as fiscal progressives, according to CNBC. Sources told CNBC that Bloomberg would likely only enter if Biden drops out of the race. 

Bloomberg, who is worth an estimated $51 billion, could choose to spend as much as $100 million on a campaign for the presidency. 

In March, the 77-year-old businessman said he would not run for president due to the high number of candidates. 

"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," Bloomberg wrote in a statement online. "But I am clear-eyed about the difficulty of winning the Democratic nomination in such a crowded field."

Bloomberg has previously been a Republican and an independent. He later became a Democrat in 2018.

As Mayor of New York City from 2002 to 2013, Bloomberg sought to push for a citywide smoking ban and to reduce the city's budget deficit. He later started to focus on making the city more environmentally friendly and improving its infrastructure. He has also pushed for bans on large-size sugary sodas and trans fat in foods. 

Bloomberg made his wealth by founding Bloomberg L.P. in 1981. The company offers financial services tools along with a news website, television channel and radio station. 

The Iowa Democratic caucuses will take place on Feb. 3, 2020.