Donald Trump is scrambling to rescue his campaign after a week in which the Republican nominee's White House hopes were set ablaze by his erratic behaviour and the discovery he may not have paid income taxes for 18 years.

Reeling from a New York Times report that Trump may have cancelled out years of income taxes by declaring a US$916 million loss on his 1995 return, his allies argued that the revelation was proof of the businessman's "genius".

And Trump tweeted: "I know our complex tax laws better than anyone who has ever run for president and am the only one who can fix them."

Surrogate Rudy Giuliani, while defending Trump, appeared to attack Democratic nominee Hillary Clinton for being a woman. He told the ABC: "This was a perfectly legal application of the tax code, and he would've been a fool not to take advantage of it. Don't you think a man who has this kind of economic genius is a lot better for the United States than a woman, and the only thing she's ever produced is a lot of work for the FBI checking out her emails?"


Governor Chris Christie told Fox News that what Trump's evasion of taxes "shows is what an absolute mess the federal tax code is, and that's why Donald Trump is the person best positioned to fix it".

Trump hopes to recover by driving a contrast between how he and Bill and Hillary Clinton made their fortunes. Clinton plans to deliver an economic address where she is expected to highlight what many voters may see as an inherently unfair tax code that allows a billionaire such as Trump to get away with legally paying no taxes.

Clinton will get a lift from President Barack Obama, first lady Michelle Obama and senators Bernie Sanders and Elizabeth Warren who are fanning out across swing states to solidify Clinton's support among young and minority voters and make the case Trump is unfit for office. Trump turned in a shaky debate performance, feuded for days with a former Latina beauty queen over her weight, slipped in polls, fired off Twitter tirades and speculated without evidence that Clinton may have cheated on her husband.

"What we're seeing is somebody who's blowing himself apart in real time," said former Republican official Peter Wehner. "It's gnawing on him that he could become what he has contempt for, and that is a loser". Mo Elleithee, a Democratic strategist, said: "Political operatives and strategists are going to study this week for generations as the textbook case of self-sabotage".

Central to Trump's candidacy has been the idea of him as a successful businessman. Political analysts said the new revelations threaten to undercut his credibility in business. Sanders told CNN: "Trump goes around and says: 'Hey, I'm worth billions! I'm a successful businessman! And I don't pay any taxes. But you - you make 15 bucks an hour - you pay the taxes, not me.' This is exactly why so many millions of Americans are frustrated, they are angry, they are disgusted."