The Supreme Court expressed concern Tuesday that allowing congressional subpoenas for tax and financial records of President Donald Trump and his businesses now would give lawmakers a “limitless” way to harass political opponents in the future.

The questions from justices during oral argument — held remotely over the telephone because of the COVID-19 pandemic — added little certainty to predictions about how the court eventually will rule in the coming months in the historic showdown between Trump and the Democratic-led House.

But a theme that emerged during questions from Chief Justice John G. Roberts Jr. — and then picked up by other key justices, including one member of the liberal wing — showed a majority see the need for courts to put some type of cap on when Congress could demand the private records of a president.

That started Tuesday when House General Counsel Doug Letter took his turn to defend the committee subpoenas that seek Trump’s personal and business financial information from auditing firm Mazars USA and two banks, Capital One and Deutsche Bank.

Trump’s attorneys at that point already had argued that the subpoenas for the president’s personal records don’t have a legitimate legislative purpose. The House argued its subpoenas are valid as long as it relates to potential legislation, and in briefs in this case pointed to several House-passed bills on money laundering and other topics.

Roberts asked Letter for a “plausible example” of a subject that is beyond any legislation that Congress could write — and Letter did not provide him with one.

Roberts then described that as a “limitless test.”

“I’m suggesting your test is really not much of a test, it’s not a limitation, and it doesn’t seem to in any way take account of the fact that we’re talking about a coordinate branch of government,” Roberts said.

Justice Samuel A. Alito Jr. and other members of the court’s conservative wing picked up on that answer. Alito, in the liveliest exchange of the argument, told Letter that “in your view there is really no protection against the use of congressional subpoenas for the purpose of preventing the harassment of a president.”

“Because the only requirement is that the subpoena be relevant to a conceivable legislative purpose, and you can’t think of a single example of a subpoena that wouldn’t meet that test,” Alito said.

Justice Neil M. Gorsuch asked Letter for a limiting principle — beyond just that legislative purpose test — that would prevent Congress from acting like a federal investigator who was not investigating a particular crime, but instead investigating a person in search of a crime to charge.

“I think as we’ve explored, that’s very, very broad and maybe limitless,” Gorsuch said.

And Justice Brett M. Kavanaugh, referring back to that “limitless authority,” asked why the courts couldn’t balance the competing interests of Congress and the president, such as a requirement that Congress show why a president’s records are critical to potential legislation.

That requirement is something that the Justice Department has proposed as part of the case.

“We’re not saying the House has no power to get out the records of the sitting president. We’re saying that it needs to satisfy a heightened standard,” Principal Deputy Solicitor General Jeffrey Wall told the justices.

“Because if it doesn’t, these requests will become routine, and that weapon in the standing arsenal of the houses of Congress, will, I think, be routinely deployed in a way that harms ... the separation of powers and undermines the presidency,” Wall said.

Justice Stephen G. Breyer, who is part of the court’s liberal wing, said one of his problems in the case is that the subpoenas go “way, way, way beyond” just Trump’s tax returns and would be a burden on a president even if they are to third-party financial institutions.

And he raised concerns about what that could mean in the future, with a reference to Sen. Joseph McCarthy, who is infamous for his investigations into communism in the United States in the 1950s.

“And the fact that what I hold today will also apply to a future Senator McCarthy asking a future Franklin Roosevelt or Harry Truman exactly the same questions, that bothers me,” Breyer said. “So, what do I do?”

Letter, for his part, pointed out that there are limits. Congress couldn’t get state secrets, documents related to executive privilege or so overwhelm the White House with subpoenas that it interferes with a president’s ability to do the job.

None of those apply to these subpoenas, Letter said, where the financial institutions haven’t said the request are a burden and Trump doesn’t have to do anything for those institutions to turn over the documents.

“In fact, some of the key documents we want, the president probably has never even seen or doesn’t even know that they exist,” Letter said. “We want to know banks’ analyses of his request for a loan, internal bank analysis.”

And Letter referred back to previous congressional inquiries into private records of a president, such as subpoenas of President Bill Clinton during the Whitewater investigation beginning in 1995.

“History really matters here, and it shows that the arguments being made here by President Trump are astonishingly — they ask you to ignore a massive amount of history,” Letter said.

Trump’s personal legal challenges to subpoenas in New York and Washington have for more than a year frustrated congressional oversight through the four subpoenas.

Trump has not prevailed in any of the lower court rulings that led to this Supreme Court challenge, and the justices on Tuesday did not appear ready to say Congress could never subpoena a president’s personal documents.