(CNN) The House Judiciary Committee on Thursday issued subpoenas to former Trump campaign manager Corey Lewandowski and a former White House official as it ramps up its investigation to determine whether to impeach President Donald Trump.

The committee issued the subpoenas Thursday to Lewandowski and former White House aide Rick Dearborn , requesting they testify publicly before the committee on September 17. Both Trump aides were cited extensively in the obstruction of justice section of special counsel Robert Mueller's report

The subpoenas don't come as a surprise — the duo was included when the committee authorized subpoenas to 12 individuals last month — but they signal the direction the committee is taking as it looks to quickly gather evidence that could lead to pursuing impeachment.

The House has not voted on a formal impeachment inquiry, but House Judiciary Chairman Jerry Nadler says his committee's investigation constitutes "formal impeachment proceedings" and the committee has a goal of deciding whether to recommend articles of impeachment by the end of the year.

"It is clear that any other American would have been prosecuted based on the evidence Special Counsel Mueller uncovered in his report," Nadler said in a statement. "Corey Lewandowski and Rick Dearborn were prominently featured in the Special Counsel's description of President Trump's efforts to obstruct justice by directing then-White House Counsel Don McGahn to fire the Special Counsel, and then by ordering him to lie about it."

Peter Chavkin, Lewandowski's attorney, questioned why Lewandowski was receiving a subpoena from the committee.

"Mr. Lewandowski has voluntarily appeared before and cooperated with Congress three times answering questions for hours. He also has spoken for hours with the Special Counsel's office. In light of this, it is fair to ask what could be gained from requiring him to appear yet again," Chavkin said, declining further comment.

A Republican Judiciary Committee aide also criticized the subpoena, accusing Democrats of wasting "more time and taxpayer dollars as Democrats demand information we already have."

So far, the committee's subpoenas have not yielded much of value beyond dozens of objections to questions about anything that happened in the Trump administration and a pair of lawsuits to try to obtain former special counsel Robert Mueller's grand jury information and testimony from former White House counsel Don McGahn.

The subpoena to Lewandowski comes as he is considering a Senate bid in New Hampshire. He's attending the President's rally Thursday night in the state, and White House aides say to expect Trump to bring up Lewandowski's potential Senate run.

By subpoenaing Lewandowski, the committee hopes it can avoid the executive privilege fight with the White House, which has directed McGahn, former White House communications director Hope Hicks and former deputy White House counsel Annie Donaldson not to answer questions beyond the 2016 election. Unlike those officials, Lewandowski never served in the Trump administration.

But it's unclear if Lewandowski will be forthcoming about the key episodes referenced in the Mueller report that will want to press him on, such as when the President instructed him to tell then-Attorney General Jeff Sessions to curtail the Mueller investigation and Lewandowski did not act on it . White House officials have been engaged in preliminary discussions about invoking executive privilege to limit Lewandowski from complying with the subpoena, according to three sources.

Lewandowski testified before the House Intelligence Committee last year behind closed doors, and he did not answer questions about anything that occurred beyond the 2016 election.

The committee last week filed a lawsuit to force McGahn to comply with its subpoena after he did not appear under subpoena for a hearing in May. The outcome of that case is likely to determine whether other former Trump officials can refuse to answer questions about the Trump White House. But it's likely to take months, if not longer, before the case is decided.

The Judiciary Committee has pointed to two episodes involving Lewandowski from the Mueller report as clear cases of obstruction of justice.

The first was when Trump told Lewandowski to ask Sessions to limit the Mueller investigation not to investigate the Trump campaign but to "move forward with investigating election meddling for future elections." Lewandowski tried to set up an in person meeting with Sessions, but did not do so, according to the special counsel.

That led to the second episode the committee cited, which also involved Dearborn. A month after making the request to Lewandowski about Sessions, the President followed up with Lewandowski and told him that if Sessions did not meet with him, he would be fired.

Lewandowski did not deliver the intended message to Sessions. Instead, he asked Dearborn to speak to Sessions, believing he would be a better messenger, the special counsel wrote.

Lewandowski gave Dearborn a typewritten version of the President's message, which "definitely raised an eyebrow" for Dearborn and made him uncomfortable, according to Mueller's team. Dearborn told Mueller he did not recall if he knew the message was from the President. Dearborn later told Lewandowski he had handled the situation but he did not follow through.

This story has been updated with additional developments Thursday.