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Billionaire Michael Bloomberg officially joined the Democratic presidential race Sunday after weeks of speculation and hedging. The move quickly garnered criticism from many within the party and within his business operations.

The former mayor of New York and media mogul said he feels he has to run because he can beat Donald Trump. Instead of focusing on early primary states like Iowa, New Hampshire and South Carolina, Bloomberg plans to focus on 'Super Tuesday' primary states, with a massive self-funded advertising campaign. Bloomberg, 77, will have to contend with the perception that he is attempting to 'buy' the election as well as controversial aspects of his mayorship, including the implementation of the controversial stop-and-frisk policy.

The namesake news service that Bloomberg runs has vowed that it won't run any investigations into any Democratic candidates, including the organisation's owner, though it will continue to run investigations into President Trump. Former editors of the organisation have labelled that decision "staggering".

With Bloomberg and the late entrance of former governor of Massachusetts, Deval Patrick, the Democratic field now stands at 18 just a few months out from the Iowa caucuses. Lecturer in US politics and foreign policy, Gorana Grgic spoke to CNBC about the struggle between progressives and moderates in the race into which Bloomberg and Patrick have waded in.