An adviser to Michael BloombergMichael Rubens BloombergBloomberg vows not to take campaign donations, presidential salary Biden on Bloomberg entering 2020 race: 'I welcome the competition' Sanders says he's 'disgusted' by Bloomberg's million ad buy MORE said the former New York City mayor won't accept political donations or a presidential salary.  

“He has never taken a political contribution in his life. He is not about to start,” Bloomberg chief adviser Howard Wolfson told The Associated Press. “He cannot be bought.”

Wolfson's comment comes as Bloomberg, a billionaire, appears poised to join the crowded 2020 Democratic presidential field. 

While current candidates have expressed that the primary race does not need one of the world's richest people, Wolfson stressed that Bloomberg's money makes him independent. 

He told the AP that Bloomberg “is wholly independent of special interests, will not take a dime in any contribution, and never has in any of his three races.”

Wolfson added that Bloomberg is willing to spend "whatever it takes to defeat Donald TrumpDonald John TrumpJane Fonda says she feels 'sad' for Trump Bloomberg vows not to take campaign donations, presidential salary Biden reveals four women he could pick as his running mate MORE.” 

Bloomberg would face an uphill battle if he runs for the Democratic nomination, since other candidates have been campaigning for months. Even though he has not officially announced his candidacy, he has purchased a $31.5 million ad blitz across several states. 

The former mayor is worth more than $54 billion according to Forbes.

News of Bloomberg's possible 2020 bid sparked strong criticism from other candidates, especially those who are on the progressive end of the democratic spectrum. Sen. Bernie SandersBernie SandersBloomberg vows not to take campaign donations, presidential salary Harris: 'I am not a socialist' Nurses across the US just endorsed Bernie Sanders — here's why MORE's campaign manager said in a statement at the time that, "More billionaires seeking more political power surely isn't the change America needs." 

Sen. Elizabeth WarrenElizabeth Ann WarrenBloomberg vows not to take campaign donations, presidential salary Georgia congresswoman shares letter to son on the anniversary of his death Harris: 'I am not a socialist' MORE (D-Mass.) welcomed Bloomberg to the race by referring him to her "Calculator for Billionaires" to show how much he'd pay under her tax plan.