WASHINGTON (AP) -- A former congressman who sponsored legislation to abolish the IRS and is now the nominee to lead that agency faced pointed questions from senators Tuesday about his past promotion of questionable tax credits, his lack of background in tax administration and the political contributions he received after being picked to lead the agency.

Former U.S. Rep. Billy Long of Missouri appeared before the Senate Finance Committee for his confirmation hearing. He was grilled by Sen. Elizabeth Warren, D-Mass., who questioned whether Long believed the president could legally direct the IRS to take away a taxpayer's tax-exempt status.

Her questions came as President Donald Trump, a Republican, has said he wants Harvard University and other non-profit organizations to lose their tax-exempt status.

Federal law prohibits the executive branch from exerting influence over taxpayer audits and other investigations.

"I'm going to follow the law," Long said, adding "I'd have to go to the lawyers," to interpret the law.

"What do you understand this law to be saying?" Warren asked. Long said he would not be able to answer. After the back and forth, Warren told Long, "You shouldn't be within a thousand miles of the directorship of the IRS."

Long told senators he had "the opportunity to make real, transformational change to an agency that needs it more than any other."

The IRS, like other federal agencies, has hemorrhaged employees due to cuts spearheaded by the Department of Government Efficiency, all while the agency churns through acting leaders as it awaits a confirmed one.

Douglas O'Donnell, the Trump administration's first acting IRS commissioner, announced his retirement in February as furor spread over DOGE gaining access to IRS taxpayer data. Melanie Krause, the second acting commissioner, resigned in April over a deal between the IRS and the Department of Homeland Security to share immigrants' tax data with Immigration and Customs Enforcement.

Gary Shapley, an IRS whistleblower who previously testified about investigations into Hunter Biden's taxes, was acting commissioner for a matter of days before being replaced by Treasury's deputy secretary, Michael Faulkender.

If confirmed, Long would be the first confirmed Trump nominee to lead the tax collection agency.

Democratic senators on the committee have railed against Long's nomination, based primarily on his past work for a firm pitching a fraud-ridden pandemic-era tax break as well as campaign contributions he received after he was nominated to serve as IRS commissioner by Trump.

After serving in Congress, Long worked with a firm that distributed the pandemic-era employee-retention tax credit. That tax credit program was eventually shut down in 2023 after then IRS Commissioner Daniel Werfel determined that it was fraudulent.

Democrats have also called for a criminal investigation into Long's connections to other alleged tax credit loopholes. The lawmakers allege that firms connected to Long -- like White River Energy Corp. -- duped investors into spending millions of dollars to purchase fake tax credits. A representative from White River did not respond to an Associated Press request for comment.

Democratic lawmakers have also written to Long and his associated firms detailing concerns with what they call unusually timed contributions made to Long's defunct 2022 Senate campaign committee shortly after he was nominated to serve as IRS commissioner by Trump.

"Bottom line, the American people have the right to know whether the future IRS commissioner is a crook," said Sen. Ron Wyden, D-Ore.

Republicans, however, were open to supporting Long. Committee Chair Sen. Mike Crapo of Idaho said he was confident Long "will be fully transparent to Congress and the American people."

Long pointed to his work in Congress as relevant experience to serve as IRS commissioner.

"By being familiar with the workings of Congress," he said, "we will have a comprehensive understanding of Congress' intent."

"I think there's a lot of wasted brain cells" at the IRS, Long said. He did not offer clarity on whether the Direct File program -- the free electronic tax return filing system developed during the Biden administration -- should be ended. But Long said it would be one of the first programs that come up for discussion if he is confirmed.