For the Republicans, Iowa went first on Jan 15, with Mr Trump, the former president, winning a landslide victory, as Ron DeSantis beat Nikki Haley to a distant second place. On Jan 23, Mr Trump comfortably defeated Ms Haley in New Hampshire and inflicted a humiliating defeat on his rival in South Carolina, her home state.
As for the Democrats, Mr Biden won the Democratic nomination in New Hampshire but Dean Phillips, his main rival, rattled the party by taking 20 per cent of the vote. The incumbent president went on to claim victories in the South Carolina and Nevada primaries, securing 96.2 per cent and 89.3 per cent of the state’s Democratic vote respectively. Hen then won the Michigan primary, in which he claimed 81 per cent of the vote.
The most recent Republican primary took place on Super Tuesday, while the next Democratic primary will be on Feb 27 in Michigan.
The first big multi-state contest was on Super Tuesday on March 5, in which 16 states and one territory went to the polls. Both the incumbent president and his predecessor swept to victory in their respective races, with Mr Trump brushing aside his last remaining challenger Nikki Haley.
Despite Ms Haley’s suprise win in Vermont, she was unable to contain the tidal wave of voters who tuned out for Mr Trump, and it was announced she would pull out of the race the following day.
As for Mr Biden, the president eased to victory in every race apart from American Samoa, where he drew with rank outsider Jason Palmer to share the delegates. The overseas US territory does not vote in the presidential election.
With Mr Trump and Mr Biden requiring just 220 and 471 delegates respectively to win the nomination from their parties, it feels all but certain that Americans will face a rematch between the two candidates come November.
While voters in the general election are in theory selecting their choice for president, in reality, they are choosing delegates for the electoral college.
All 50 US states and Washington DC have a set number of electors in the electoral college, roughly proportional to the population size of the state.
