Congress’ investigative arm may be about to add a new wrinkle into the Senate’s impeachment trial of President Donald Trump sparked by the nearly two-month holdup of Ukraine security assistance last year, which Democrats charge Trump orchestrated to extract political favors.

As early as this week, the Government Accountability Office could release its legal opinion on whether Trump and senior White House officials violated the Nixon-era budget law that requires executive branch agencies to spend appropriated funds according to lawmakers’ wishes.

Sen. Chris Van Hollen, D-Md., who initially requested the GAO ruling last year, said he believes that Trump violated the 1974 law aimed at preventing such presidential “impoundments.” But he wouldn’t go so far as to label that an impeachable offense.

“The House charges of abuse of power do not relate directly to the [1974 budget law], they relate to the president of the United States improperly using taxpayer funds to . . . pressure Ukraine into interfering in the 2020 election on his behalf,” he said. “But look, this is all part of the picture that’s being painted. But I don’t want to elaborate further until we see what the GAO opinion is.”

Nevertheless, in a Dec. 23 letter to GAO, Van Hollen wrote that Trump’s withholding of the aid was illegal and part of a “scheme” to, as the House impeachment inquiry charged, “use the powers of his office to solicit foreign interference on his behalf in the 2020 election.”