Hillary Clinton
Hillary ClintonReuters

Hours before polls open for Election Day, the presidential candidates continued to attack one another in final rallies on Monday.

To that end, Democratic presidential candidate Hillary Clinton told Americans that there is one thing they won't see before they go to the polls on Tuesday: her Republican rival Donald Trump's tax returns.

"I'm still pondering, just pondering, how anybody can lose $1 billion in one year, especially when you're running casinos,” Clinton told supporters at a rally in Allendale, Michigan, on Monday afternoon, according to Politico.

“But that will be one of the mysteries in this campaign, because he's not going to release his tax returns between now and the time you start voting and that sort of suggests there must something terrible in those tax returns, because everyone else for over 40 years has released them,” she continued.

Clinton has repeatedly criticized Trump for his refusal to release his tax returns, breaking with decades of tradition, and urged him to do so.

The Republican nominee has explained he declined to release his returns because he is under a routine audit from the Internal Revenue Service.

The New York Times obtained snippets of Trump’s returns from the 1990s, hinting he might have avoided paying taxes for nearly two decades.

According to the report early last month, Trump declared a $916 million loss on his 1995 income tax returns, a deduction so large it might have enabled him to avoid paying any federal income tax for up to 18 years.

Meanwhile, Trump on Monday criticized Clinton over her private email server, a day after FBI Director James Comey announced the agency had not changed its opinion about not pressing charges against Clinton in the case.

“Did you ever see a mess like this?” Trump said at a rally in Raleigh, North Carolina. “Did you ever see? Of course, the FBI, the director, was obviously under tremendous pressure.”

“So they went through 650,000 emails in eight days. Yeah, right,” Trump added incredulously. “So sad what’s going on?”

He went on to hint that the FBI doesn’t need any additional evidence to convict Clinton of a crime.

“She still deleted them after getting a subpoena from Congress. I mean, that’s a crime!” Trump exclaimed. “What happened? That’s a crime! You don’t even need the new stuff. She shouldn’t be allowed to run.”