(Bloomberg) -- U.S. Chief Justice John Roberts sent mixed signals on subpoenas by House Democrats for President Donald Trump’s financial information, as the Supreme Court began hearing arguments in a constitutional showdown that could affect the November election.

Roberts questioned Trump’s contention that lawmakers lacked a legitimate legislative purpose for the subpoenas to his banks and accountants, asking the president’s lawyer whether the court should be “probing the mental processes” of lawmakers.

But Roberts also said a lawyer for the House was proposing a “limitless test” that didn’t “take account of the fact that we’re talking about a coordinate branch of government, the executive branch.”

The Supreme Court is hearing back-to-back telephone arguments Tuesday on Trump’s efforts to stop his banks and accountants from complying with subpoenas they have received from House Democrats and a New York prosecutor. Roberts’s vote is likely to be pivotal in both cases.

The court’s rulings could determine whether the president’s tax returns become public before November, and whether Trump faces an accelerated criminal investigation in New York.

Many of the other justices suggested they would divide along ideological lines, with the court’s liberals aiming the toughest questions at Trump’s defenders.

(Adds in fifth paragraph that justices seemed ideologically divided)

©2020 Bloomberg L.P.