As Steven Rosenthal, senior fellow at the Tax Policy Center of the Urban Institute and the Brookings Institution, told Salon: “There is no legal impediment to somebody who is under audit releasing taxes and […] the IRS audits every single president and vice president on their tax returns. If he continues to follow the policy of not releasing his tax returns while under audit, then we’ll never see any of these tax returns.”

Trump’s stubborn refusal to release his tax returns is earning him ire from Democrats and Republicans alike and threatening his long-promised tax reform, the New York Times reported Tuesday. “[A] growing roster of more than a dozen Republican lawmakers now say Mr. Trump should release them,” the newspaper notes.

Democrats have mobilized multiple efforts to attempt to force Trump to release his taxes, and tell the Times that further maneuvering is planned.

“If he doesn’t release his returns, it is going to make it much more difficult to get tax reform done,” Senate Minority Leader Chuck Schumer (D-N.Y.) told the Times, pointing out Trump’s potential conflicts of interest surrounding the estate tax and real estate taxes. “It’s in his own self-interest.”

“When they talk about tax reform, are they talking about cutting Donald Trump’s taxes by millions of dollars a year?” Ezra Levin, a member of the Tax March executive committee and a leader in the Indivisible movement, which has elevated the call, wondered to the Times. “We don’t know.”

Indeed, as former White House counsel and Citizens for Ethics and Responsibility in Washington (CREW) director Norman Eisen wrote last week:

At a minimum, before this administration even thinks of proposing any changes to the tax code, we should see what tax code provisions the president himself has been and is taking advantage of, and how much tax he has paid in the past few years. Otherwise we are bound to end up with a deal where the rest of us pay yet more tax while he, and probably his business partners and political allies, pay less.

“The ‘art of the deal’ for him, perhaps, but for the rest of us it’s the ‘art of the steal,'” Eisen quipped.

The Patriotic Millionaires, a progressive advocacy group of high net-worth individuals, also joined the chorus of Americans demanding Trump’s taxes Tuesday. “I believe our government has important responsibilities to help make this country a good place to live, not to just cut my taxes at the expense of the low income and middle class,” said Rich Boberg, a member of the group and an entrepreneur.

“I’m deeply concerned the upcoming tax plan will be used as just another opportunity to cut my taxes and the taxes of other wealthy people, making our country a worse place to live for everybody,” Boberg added.

The New York Times further added that “[b]eyond the politics of Mr. Trump’s returns, lawmakers do not want to pass an overhaul of the tax code that unwittingly enriches the commander in chief and his progeny.”

The list of politicians calling for Trump to release his returns “grows almost daily,” observed the Times. And the swelling campaign is having an effect.

Trump’s Treasury Secretary, former Goldman Sachs executive Steven Mnuchin, admitted to the Financial Times Monday that the administration’s ambitious August deadline for tax overhaul is unlikely to pan out.

Politico reported that “Mnuchin told the Financial Times that the timeline is ‘highly aggressive to not realistic at this point.'”

And public opinion is not on Trump’s side, it seems. On Monday, Sen. Tom Cotton (R-Ark.), was repeatedly and loudly booed after he attempted to defend Trump’s refusal to release his returns. “The former president showed us his birth certificate! My God,” exclaimed one frustrated attendee in an interview with CNN.

Watch Cotton’s defense of Trump—and the crowd’s reaction—here: