WASHINGTON (AP) — House Republicans will issue subpoenas on Wednesday to members of President Joe Biden’s family, taking their most aggressive step yet in an impeachment inquiry bitterly opposed by Democrats that is testing the reach of congressional oversight powers.

The subpoenas were expected to be issued later Wednesday afternoon. The long-awaited move by Rep. James Comer, the chairman of the House Oversight Committee, to subpoena the president’s son Hunter and his brother James comes as Republicans look to gain ground in their nearly yearlong investigation. So far, they have failed to uncover evidence directly implicating the president in any wrongdoing.

But Republicans say the evidence trail they have uncovered paints a troubling picture of “influence peddling” by Biden’s family in their business dealings, particularly with clients overseas.

“Now, the House Oversight Committee is going to bring in members of the Biden family and their associates to question them on this record of evidence,” Comer, of Kentucky, said in a statement.

The stakes are exceedingly high, as the inquiry could result in Republicans bringing impeachment charges against Biden, the ultimate penalty for what the U.S. Constitution describes as “high crimes and misdemeanors.”

The subpoenas demand that Hunter Biden and James Biden as well as former business associate Rob Walker appear before the Oversight Committee for a deposition. Lawmakers also requested that James Biden’s wife, Sara Biden, and Hallie Biden, the wife of the president’s deceased son Beau, appear voluntarily for transcribed interviews.

Requests for comment from Hunter Biden, who lives in California, and James Biden, who’s from Royal Oak, Maryland, were not immediately returned.

Both the White House and the Biden family’s personal lawyers have dismissed the investigation as a political ploy aimed at hurting the Democratic president. They say the probe is a blatant attempt to help former President Donald Trump, the early front-runner for the 2024 GOP presidential nomination, as he runs again for the White House.

Hunter Biden’s attorney Abbe Lowell said the investigation has been full of “worn-out, false, baseless, or debunked claims.” In a letter to House Speaker Mike Johnson on Wednesday morning, Lowell urged the new speaker to rein in the “partisan political games.”

Johnson, now settling into the speakership after replacing Kevin McCarthy as the top Republican in the House, has given his blessing to the inquiry and has hinted that a decision could come soon on whether to pursue articles of impeachment against Biden.

“I think we have a constitutional responsibility to follow this truth where it leads,” Johnson told Fox News Channel recently. He also said in a separate Fox interview that he would support Comer’s decision to subpoena the president’s son, saying “desperate times call for desperate measures, and that perhaps is overdue.”

Since January, Republicans have been investigating the Biden family for what they claim is a pattern of “influence peddling” spanning back to when Biden was Barack Obama’s vice president. Comer claims the committee had “uncovered a mountain of evidence” that he said would show how Biden abused his power and repeatedly lied about a “wall” between his political position and his son’s private business dealings.

While questions have arisen about the ethics surrounding the Biden family’s international business, no evidence has emerged to prove that Joe Biden, in his current or previous office, abused his role or accepted bribes.