How to register as a presidential candidate for the 2020 US election

Kamala Harris the latest Democrat to come forward as challenger to Donald Trump

California senator and former state attorney-general Kamala Harris is the latest Democrat to declare her candidacy for the 2020 presidential election.

Ms Harris, who made headlines challenging Trump administration appointees Jeff Sessions and Brett Kavanaugh as part of Senate judiciary committees, faces a crowded field in her bid to challenge the embattled incumbent but would represent a progressive choice should she secure the nomination.

So far, six other members of her party have declared their intention to run, with many more high-profile candidates thought to be waiting in the wings, from stalwarts Joe Biden, Hillary Clinton and John Kerry to promising newcomers like Texas congressman Beto O’Rourke.

In theory, there are only three requirements a would-be nominee must meet to be eligible to declare their candidacy for the position of “Leader of the Free World”.

They must be a natural-born citizen of the US, at least 35 years of age and resident in the country for 14 years or more.

If they meet those three qualifying conditions, they are free to announce a presidential bid at any time, alligning themselves with the Democratic or Republican cause.

Right-wing conspiracy theorists, Donald Trump among them, used the first of these criteria to question Barack Obama's eligibility in the run-up to the 2008 presidential election, alleging the Illinois senator had really been born in Kenya, not Hawaii, and therefore had no right to run, a fabrication the 44th president would send up with glee at future White House Correspondents' Dinners.

Once a candidate receives more than $5,000 (£3,870) in donations or spends in excess of that amount on their campaign, they are required to register with the Federal Election Commission, filing a Statement of Candidacy authorising a committee to fundraise and knock on doors on their behalf.

The aspiring president must then pass through state primary elections, where their suitability is voted on by party members.

They will subsequently find themselves under consideration at caucases - open to all or exclusive to party members - where supporters of the candidate congregate to make the case for their man or woman ahead of another vote.

Crucial at this stage is winning the support of delegates, who will go on to represent the state's candidate at national party conventions. The person winning the nomination from the greatest number of delegates wins.

The chosen candidates from each state are finally brought together at convention, where presidential and vice-presidential nominees are confirmed. This is usually done by coronating the person backed by the most delegates but if none holds a clear majority, a final vote will be held to determine who should be the party's bet for the White House.

After all that, it's time to start the exhausting, months-long business of campaigning nationwide in earnest, the candidate touring each of the 50 states to persuade a population of 326m that they alone have the people's best interests at heart and all the answers to the nation's innumerable social and economic problems.