On Tuesday 3 November, 2020, the US will choose whether to give Donald Trump a second term as the world’s most powerful leader – or vote for a change at the top.

It might still seem a long way off, but the campaign wagon has been rumbling along for months. While the Democrat nominee hopefuls will be whittled down in the primaries, starting in February, some of them launched their campaigns as early as January 2019.

To the rest of the world, the 18-month-long presidential race may seem unusual – compare it to a 25-day limit on election campaigning in the UK. And there are plenty of hurdles potential candidates have to overcome first, as the below chart shows.

Image: usa.gov

Here are five things you need to know about the US presidential election campaign and the country’s former presidents.

1. It takes as long as it takes

Unlike other countries, America has no legally defined set term for fundraising and campaigning – meaning the Democratic hopefuls have been staggering their campaign launches for months.

Donald Trump doesn’t become the official Republican candidate until summer 2020, when his party puts him forward, and he may have at least one challenge for the top job, from former Massachusetts Governor Bill Weld.

Trump’s been preparing to run for a second term since January 2017, when he submitted the paperwork to stand again on the day he walked into the Oval Office. It meant he could start accepting campaign contributions from that day. He filed his statement of candidacy in June.

Campaigning will intensify once both parties have chosen their presidential nominee, when they’ll start crisscrossing the country holding rallies to win support.

2. There are 3 requirements for candidates

The US constitution sets requirements for presidential candidates, which are:

You have to be over 35

You have to be a ‘natural-born’ US citizen

You have to have been a US resident for at least 14 years

U.S. President Ronald Reagan (R) shakes hands at his first meeting with Soviet leader Mikhail Gorbachev to sign an arms treaty in Geneva, in this November 19, 1985 file photo. The two leaders met for the first time to hold talks on international diplomatic relations and the arms race.  REUTERS/Denis Paquin/Files (SWITZERLAND - Tags: POLITICS PROFILE TPX IMAGES OF THE DAY)ATTENTION EDITORS - THIS PICTURE IS PART OF PACKAGE '30 YEARS OF REUTERS PICTURES'TO FIND ALL 56 IMAGES SEARCH '30 YEARS' - LM2EB2A0WGZ01
Image: Denis Paquin/Reuters

3. A lot of former presidents studied law

Donald Trump carved out a career as a businessman and reality TV star before becoming the 45th “POTUS” and Ronald Reagan was a film star before moving into the White House as the 40th president. But they’re the exceptions.

More than half the US presidents since 1789 have been law graduates or lawyers, including Trump’s predecessor Barack Obama.

4. All of them have been men – and one has been in office twice

While Trump is the 45th president, there have actually only been 44 men (and no women to date) in the post, because one – lawyer Grover Cleveland –- was the 22nd and 24th.

The constitution’s 22nd amendment stipulates that “no person shall be elected to the office of President more than twice”.

One father-son duo (George HW Bush and George W Bush) has been in power – as the 41st and 43rd presidents respectively.

George W. Bush is shown with his father, future President George Bush and mother, future first lady Barbara Bush in Rye, New York, in this file photo taken during the summer of 1955. With the Republican convention set to begin in Philadelphia on July 31, the political focus has centered on who Republican presidential candidate George W. Bush will pick to be his running mate.CM - RP2DRHYTFQAA
Image: REUTERS

5. It’s an expensive business

Advertising, travel and rallies play a huge part in election campaigns, and they don’t come cheap.

According to the Center for Responsive Politics, the 2016 presidential elections cost $1.5 billion, although, as the below chart shows, President Trump’s funding was less than that of his opponent Hillary Clinton.

Image: Center for Responsive Politics

The Federal Election Commission keeps a tally of how much each candidate has raised. In the first quarter of 2019, Donald Trump raised $30.3 million, $10 million more than Democrat Bernie Sanders.