How the dirtiest US election campaign of modern times was fought

Democratic presidential nominee Hillary Clinton, right, speaks as Republican presidential nominee Donald Trump listens during the second presidential debate at Washington University. Photo / AP

As President Barack Obama's second term began to draw to a close, the predictions came in thick and fast.

This would be the year of the establishment Titans: an epic struggle between the Clinton and the Bush dynasties over who would rule for a second time.

But then Donald Trump swept in, and threw the rule book away.

He blasted through political decorum, insulted swathes of the nation, smashed through pillars of the process, and is still locked in a hair's breadth battle for the White House.

It was a race that brought presidential politics to new lows, and proved to future White House hopefuls that there is nowhere you cannot go in the quest for power.

It was an election that veered from the offensive to the bizarre.

Hillary Clinton, the Democratic nominee spend part of the time under investigation from the FBI for the use of her private email server she was secretary of state.

And Mr Trump was found guilty of massive tax avoidance. His name was mentioned in stories about the Russian mob. Twelve women said they had been sexually assaulted by the Republican nominee. And yet he still survived to fight her on election day.

It began at the foot of a golden escalator in Trump Tower, Donald Trump's glitzy New York headquarters. Mr Trump, a well-known casino billionaire and television show entertainer, launched his presidential campaign in June 2015 to collective guffaws from the political elite. "We are going to make our country great again," he said.

Mr Trump announced that he would build a giant wall to keep Mexicans out - and make Mexico pay for it. "When Mexico sends its people," he claimed, "They're bringing drugs. They're bringing crime. They're rapists."

The most bizarre US election season in recent memory had begun. On the other side of the aisle, there was little jostling for the Democratic presidential nomination.

Few wanted to challenge former first lady and secretary of state, Hillary Clinton. But she ended up with a bigger battle than she anticipated when Bernie Sanders, the septuagenarian socialist senator from Vermont, loped out from a side door of congress and announced to a small cluster of journalists on the lawn that he was going to run.

Young people began appearing at his rallies, attracted by his opposition to big money America and the promise of free university tuition.

With Mr Sanders whipping his supporters into a frenzy, Mrs Clinton found herself parodied on US comedy shows for a lack of charisma.

Her slogans "I'm With Her" and "Stronger Together" failed to resonate like Mr Sanders' "Feel the Bern". Mr Sanders pulled off an early upset in Iowa in the primary contest and stunned pollsters when he also won Michigan. Meanwhile, the Republican primary was being shaken up too.

Mr Trump was abrasive, braggadocio and ineloquent - and gaining ground. Scandals that would have killed other presidential campaigns, such as a call for a temporary ban on Muslims entering the US, only saw him rise in the polls.

In the primary debates, he joked about the size of his genitalia and accused moderator Megyn Kelly of asking unfair questions because she had been menstruating. He also used the debates to annihilate his opponents with crippling monikers which, once uttered, were true enough to stick.

Jeb Bush, the brother and son of former presidents who believed his time had come, was dubbed "low energy Jeb" and duly faded away, along with "Little Marco" Rubio, and "Lyin' Ted" Cruz. A field of 17 Republicans was eventually whittled down to one and it became official: Mr Trump was the Republican presidential nominee.

Mrs Clinton also won her primary race, but emerged bruised from the fight. As well as the battle with Mr Sanders, she faced an FBI investigation into her use of a private email server while she was secretary of state.

In July 2016 she was cleared of criminal wrongdoing, but FBI director James Comey's stunning rebuke that she was "extremely careless" was useful fodder for her rival.

She emerged as the second most unpopular major party presidential nominee in modern American history - Mr Trump being first.

At a September 11 memorial service, Mrs Clinton was filmed collapsing and had to be bundled into a car, leading to wild rumours about her health. Supporters of Mr Trump suggested she had a brain tumour. Mrs Clinton later explained she had pneumonia.

By the first presidential debate Mrs Clinton had learned that she needed to get down in the dirt. She pummelled her opponent, calling him a sexist, a racist, and tax dodger. She also introduced the story of Alicia Machado, a former Miss Universe who Mr Trump had called "Miss Piggy" when she put on weight.

It was a turning point, and polls showed her starting to build a lead. Just as it seemed the campaign season could not get more sordid, a sudden appearance of a 2005 tape revealed Mr Trump making crude remarks about women and boasting how his fame meant he could "grab them by the pussy".

Mr Trump dismissed the remarks as "locker room talk." Then around a dozen women then came forward to say they had been victims of Mr Trump's unwanted advances.

At the second debate, Mr Trump tried to hit back by bringing up sexual allegations against Mrs Clinton's husband, seating the accusers in the front row. But the damage to his campaign was done. Mrs Clinton's poise in such an extraordinary situation won the respect, if not the enthusiasm, of many voters, and it seemed that, finally, the election was hers.

In an attempt to seem presidential, Mr Trump gave a speech at Gettysburg to lay out a plan for his first 100 days in the Oval office, but he scuppered the event by promising to sue the women who accused him of sexual assault. As desperation set in, Mr Trump began ranting that the election was "rigged".

In the final debate, he declared that he would keep the country "in suspense" and might not accept the result. Mrs Clinton then suffered the ultimate "October surprise".

With just 11 days to go, Mr Comey announced that the FBI was scrutinising new emails that were "pertinent" to the previous investigation of Mrs Clinton's private server. They were discovered on the computer of Anthony Weiner, the former congressman accuses of sending sexually explicit messages to a 15-year-old girl who was married to close Clinton aide, Huma Abedin.

Mrs Clinton's poll numbers started to turn; Mr Trump performed at his rallies with glee. Then, in another shock just two days before the election, Mr Comey revealed that nothing incriminating had been found in the emails.

Mrs Clinton was in the clear. As the campaign drew to a close, many Americans were reportedly seeking therapy for high levels of stress brought on by the election.

And after so many rules have been broken, American politics will never be the same again.