Trump agreed Wednesday to the one-on-one debate suggestion and hasn't backed down yet, but he has set some terms.
He stipulated Thursday that he'd "want a lot of money to be put up for charity" in order to make the debate happen.
During a press conference in North Dakota, Trump said "if we can raise for maybe women's health issues or something, if we can raise $10 million or $15 million for charity," then it could work.
"I understand the television business very well. I think we’d get very high ratings. It should be in a big arena somewhere. And we could have a lot of fun with it," Trump added.
For his part, Sanders, who had initiated the challenge via a question he submitted to Jimmy Kimmel, said Thursday he's "excited" about the prospect, but "we will see if he stays with it."
At a rally in Pomona, California, Sanders went on to lay out some of the "very simple questions" he would ask the presumptive Republican nominee, including topics like the federal minimum wage, wealth disparity, whether or not Trump thinks climate change is a hoax, and "why he thinks trying to divide us up is good for America."
ABC News political analyst Matthew Dowd sees the whole debate over a possible debate as a win for both sides.
"I think it's a really smart move on both their parts," Dowd said on "Good Morning America" today.
"These are two people, especially Donald Trump, who don't play by traditional rules. Donald Trump's coalesced the Republican Party - he's got that - now he's moving on to the independents.
"It highlights Donald Trump's victories and it undermines Hillary Clinton as she's not able to turn towards the general election," Dowd said.
As for Hillary Clinton, the notion of a Trump-Sanders fight night "was a joke," and she says she's moving on.
"I'm going to look forward to debating Donald Trump," she said Thursday in California.