Democrats on the House Ways and Means Committee said it would be months before they definitively try to obtain President Donald Trump’s tax returns, after a lengthy hearing Thursday to hear from tax and constitutional law experts.

“This is not the end. This is just the beginning,” Ways and Means Oversight Subcommittee Chairman John Lewis of Georgia said, making it clear there would be more hearings and examination of the sensitive matter.

New Jersey Democrat Bill Pascrell Jr. echoed previous comments from Ways and Means Chairman Richard E. Neal that the process would be lengthy and methodical.

“We’re moving along in a diligent way and a very deliberative way and we’re going to get the answers,” Pascrell told reporters after the hearing.

Pascrell estimated it would be two or three months before Neal even exercised his powers under the tax code to tell the Treasury secretary to provide the president’s tax returns to him.

“We got a plan and we’re going to be deliberate about that plan,” Pascrell said.

If the chairman of one of the tax committees in Congress asks for the president’s tax returns, there is “no wiggle room” for the Treasury secretary to deny the request, a law professor told panel members Thursday.

A refusal to provide the tax returns would be “uncharted territory,” said George K. Yin, a professor at the University of Virginia School of Law and former chief of staff of the Joint Committee on Taxation.

During the hearing, Lewis called the topic one “of great interest to the American people.” President Donald Trump declined to release his tax returns during the 2016 campaign; candidates aren’t required by law to do so, but it’s been customary for them to release their returns to the public anyway.

Yin said that while the tax code bars revealing returns without the filer’s permission, tax returns can be shared with Congress. But a Ways and Means chairman must have “a legitimate purpose” to take such an action because of the risk of disclosure in sharing the documents with the larger body, he added. 

Pennsylvania Republican Mike Kelly, the subcommittee’s ranking member, said tax code rules that allow the Ways and Means panel to get the president’s tax returns were also written to ensure the privacy of all Americans’ returns.

For the committee to use its right to demand the president’s tax returns would be “such an abuse of power” and it “would open up Pandora’s box,” he said. 

“Where does it end?” Kelly asked. “What about the tax returns of the speaker?

The last candidate to capture more than 10 percent of the vote who didn’t disclose his tax returns was independent candidate Ross Perot in 1992, according to a Congressional Research Service report. The last major party candidate to not disclose tax returns was Democrat George McGovern in 1972, although President Richard Nixon disclosed his returns.

In 1976, both major party candidates disclosed tax returns for the first time, according to CRS, though President Gerald Ford released only “partial” tax returns. Democrat Jimmy Carter disclosed “full” returns.

Since then, every president from Carter to Barack Obama — including Ronald Reagan, George H.W. Bush, Bill Clinton, and George W. Bush — all disclosed their returns.

The last vice presidential candidate of a major party to not publicly provide tax returns was Ford’s 1976 running mate, former Sen. Robert Dole. During the 2016 campaign, Vice President Mike Pence released 10 years of his tax returns covering 2006-2015.

Indiana Republican Jackie Walorski said Thursday that “the level of disclosure varies widely” among the presidents from Ford to Obama who did release their returns. And tax returns of a business owned by a president have not been disclosed, she pointed out.

Another witness at the hearing, Joseph J. Thorndike, director of the Tax History Project, agreed that presidential candidates disclosing their tax returns is “tradition, not a law.”

He noted, though, that 2012 Republican presidential candidate — and current senator — Mitt Romney disclosed some tax return information from trusts in which he had ownership.

“The American people deserve to know whether their executive stands to personally benefit” or be influenced because of his business dealings, California Democrat Linda T. Sanchez said.

Illinois GOP Rep. Darin LaHood quizzed the panel of experts on whether a chairman of the Ways and Means Committee has ever sought a president’s tax return while there was an ongoing Justice Department independent counsel investigation. None could think of an example.

“It’s confusing to me,” LaHood said. “It’s never been done. This seems to me like a waste of time and resources.”