US President Donald Trump in 2016 became the first since 1969 to win an election without releasing his tax returns, claiming there was “nothing to learn” from those documents.
On Sunday, The New York Times published an investigation showing Mr Trump did not pay any federal taxes in 10 of 15 years since 2000, and only $750 in 2016 and in 2017.
The report showed Mr Trump declared $1.4 billion in losses in 2009 and owes $421 million in loans due by 2024.
If he wins a second term, The New York Times said "his lenders could be placed in the unprecedented position of weighing whether to foreclose on a sitting president".
And despite pledging to suspend foreign operations for his business and avoid conflict of interest as president, those operations continued, the Times said.
In 2017 and 2018, Mr Trump received $73m from foreign operations, including $3m from the Philippines, $1m from Turkey and $2.m from India.
Mr Trump and his campaign called the report “fabrications” and “fake news".
But without the president releasing his returns, the argument is hard to sustain, election analyst and statistician Nate Silver wrote:
Since 1933, with the exception of a brief pause in the 1950s and '60s, successive US presidents from Franklin Roosevelt have released their tax returns.
With the bombshell dropping on the eve of the first presidential debate between Mr Trump and Democratic nominee Joe Biden, the incumbent’s tax will be a topic.
It also debunks the image of the “very stable genius” that Mr Trump took on as a businessman and property mogul in 2016.
“The taxes are secondary,” author Jay Caruso tweeted.
"The brilliant businessman image was all a facade, no matter how much gold-plated [things] Trump had in his Trump Tower apartment. He sold people a bill of goods."
The leaked returns, if true, also show Mr Trump claimed $70,000 in tax deductions for hair styling, which is unlikely to go down well with some of his supporters.
As Mr Biden makes inroads among the working class in Wisconsin, Iowa and Michigan – states that Hillary Clinton lost in 2016 – the image of Mr Trump paying little to nothing in federal taxes could be harmful among this demographic.
The returns also raise the question of conflict of interest with countries such as the Philippines, India and Turkey, which he may have to answer at the debate.
But as in 2016 and with a highly polarised electorate, it is unlikely that these documents will be a make-or-break moment in the US election.
Mr Trump and Mr Biden have overridden scandals and gaffes throughout their political lives and have shown resilience among the core supporting base of both parties.
With 36 days left before the vote on November 3, the tax revelations will help Mr Biden to go on the offensive.
It also steals the limelight from a more favourable headline for Mr Trump after the Supreme Court nomination of conservative judge Amy Coney Barrett on Saturday.