Former New York Mayor Michael Bloomberg is considering becoming the second billionaire to enter the 2016 presidential race.

Sources close to Bloomberg told The New York Times that he is considering mounting an independent bid for the White House because he is annoyed with the meteoric rise of Republican Donald Trump, the shortcomings of Democratic hopeful Hillary Clinton and the success of Sen. Bernie Sanders in the Democratic race.

Bloomberg, 73, who served as mayor of New York from 2002-2013, has said repeatedly that he would not run for president, but his aide insisted that "He's definitely thinking about [running for president] more than he was," according to ABC News.

He's much more likely to enter the race if Trump or Sen. Ted Cruz become the GOP's nominee and Sanders becomes the Democratic nominee, according to NBC News.

An adviser said that Bloomberg is upset over extremist rhetoric in the Republican field, as well as Clinton's leftward turn as she attempts to counter an unexpected surge from Sanders, a self-described democratic socialist from Vermont, reported The Wall Street Journal.

Bloomberg reportedly commissioned a poll in December to gauge how he might perform against Trump and Clinton, and he plans to conduct another poll after the New Hampshire primary on Feb. 9 to see whether there is a viable opening for him, two people familiar with his plans told the Times.

He has hired a consultant to conduct research on how to get his name on all 50 ballots in time and has instructed advisers to begin studying past third party campaigns and drawing up a blueprint for a run.

Bloomberg has reportedly set a deadline of early March and said that he would be willing to spend at least $1 billion of his fortune to get elected.