Democrats will hold their first hearing Thursday on the importance of presidents disclosing their tax returns, setting up a showdown between the House and the Treasury Department over President Donald Trump's own returns.

During the 2016 campaign, Trump defied decades of precedent by not releasing his personal returns , fueling questions about how his financial interests could impact his decisions as President.

The hearing before a House Ways and Means subcommittee panel will focus on a provision in the Democrats' sweeping ethics reform legislation -- H.R. 1 -- that requires future presidential candidates and the President to release 10 years of tax returns. But the discussion surrounding presidential disclosure will no doubt cast the spotlight directly on Trump.

Democrats hope that the hearing will help build their case for why the American people need to see Trump's tax returns. Some of the witnesses — a crew of tax and ethics experts — have urged Congress to demand them, arguing that it would provide answers to whether the President, who has maintained ownership of his business, is benefiting from public office .

"Is he profiting from his position?" asked Steven M. Rosenthal, a witness at Thursday's hearing and a senior fellow at the Urban Brookings Tax Policy Center, in a column last year. "Is the public harmed?"

Joining Rosenthal at Thursday's hearing will be George Yin, a professor at the University of Virginia School of Law and former chief of staff for the Joint Committee on Taxation; Noah Bookbinder, executive director for the Citizens for Responsibility and Ethics and Joe Thorndike, executive director at the Tax History Project.

"If you think this is important, then you should require its release," said Thorndike in an interview with CNN. "If you are not prepared to require its release then you don't really think that it's very important."

While tax experts say that Congress has the power to obtain Trump's returns, there's an open question over whether it can then publicly release them without the president's consent.

Meanwhile Republicans have dismissed the Democratic effort as a partisan witch hunt.

"I would expect the President to use every legal means he can to keep that from happening. I don't know what those legal means are, I just would expect him to use every legal means," said Senate Finance Committee Chairman Chuck Grassley, an Iowa Republican. "I thought we learned a lesson about the politicization of the IRS when Nixon was President and that is why 6103 was passed, so what are the Democrats doing trying to use the IRS as a political tool? It's just as wrong (as) if Nixon were doing it."

The chairman of the House Ways and Means Committee has said he plans to request Trump's returns using IRS code 6103, a provision that Democrats say allows the chairman of the House Ways and Means committee to request Trump's tax returns. The law states that the chairmen of the Senate Finance Committee and House Ways and Means committee each have the power to request taxpayer information and states that "the secretary shall furnish such committee with any return or return information specified in such request."

But, the fight over Trump's returns is just beginning. Trump's lawyer Rudy Giuliani has made it clear that the President intends to fight any request in court. And Democrats on Capitol Hill anticipate that the Treasury will take its time in reviewing any request.

"Treasury could slow-walk this entire process," a former senior IRS official told CNN last week. "There is nothing in the statute that specifies when the agency must comply with the request."

In January, Neal told CNN that he is "judiciously" pursuing Trump's tax returns . "I think the idea here is to avoid the emotion of the moment and make sure that the product stands up under critical analysis," he said. "And it will."

On Wednesday, House Minority Leader Kevin McCarthy said he views the House Ways and Means Committee's ability to seek Trump's tax returns as "political."

"I think Ways and Means should focus their time making sure of how strong this economy is today, of how we can make it stronger," said McCarthy, a California Republican. "I think that's the focus of the American people would like to see going forward, and that's the focus we'd have as well."

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