House Republicans issued subpoenas 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 long-awaited move by Rep. James Comer, the chairman of the House Oversight Committee, to subpoena the president’s son Hunter and 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 by mid-December. 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.

Hunter Biden’s attorney Abbe Lowell called the subpoenas “yet another political stunt” and said the investigation has been full of “worn-out, false, baseless, or debunked claims.”

“Nevertheless, Hunter is eager to have the opportunity, in a public forum and at the right time, to discuss these matters with the Committee,” he added.

An attorney for James Biden said there was no justification for the subpoena as the committee had already reviewed private bank records and transactions between the two brothers. The committee found records of two loans that took place when Biden was not in office or a candidate for president.

“There is nothing more to those transactions, and there is nothing wrong with them,” attorney Paul Fishman said in a statement late Wednesday. “And Jim Biden has never involved his brother in his business dealings.”

The White House has continuously 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.

“These subpoenas and interview requests are yet further proof that this sham impeachment inquiry is driven only by the demands of the vengeful and prevaricating Donald Trump,” Rep. Jamie Raskin, the top Democrat on the Oversight Committee, said in a statement.

The impeachment inquiry slowed down in early October after Kevin McCarthy was ousted as speaker by a handful of fellow Republicans, stalling legislative business and congressional investigations as the conference spent weeks deliberating his replacement before electing Mike Johnson late last month.

Now settling into the speakership, Johnson, of Louisiana, 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.”

In a letter to Johnson on Wednesday morning, Lowell had urged the new speaker to rein in the “partisan political games.”

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.

Over the summer, Republicans expanded their investigation to include oversight of the ongoing Justice Department investigation into Hunter Biden and allegations that the case was plagued with interference.

One focus of the congressional inquiry has been whether the now-special counsel overseeing the case, David Weiss, had full authority to bring charges against the president’s younger son. In an unprecedented interview Tuesday, Weiss told lawmakers that he was the “decision-maker” in a yearslong case into Hunter Biden’s taxes and gun use.

No one at the Justice Department, including U.S. attorneys or the tax division, blocked or prevented him from pursuing charges or taking other necessary steps in the investigation, Weiss said.

The five-year investigation into Hunter Biden had been expected to end with a plea deal this summer, but it imploded during a July plea hearing. Weiss has now charged the president’s son with three firearms felonies related to the 2018 purchase of a gun during a period Hunter Biden has acknowledged being addicted to drugs. No new tax charges have been filed.