The pro-democracy watchdog Common Cause on Tuesday sent a letter to congressional lawmakers calling for the impeachment of U.S. Attorney General William Barr.

Sent to every member of both the U.S. House and U.S. Senate, the letter (pdf) charges that Barr—appointed by President Donald Trump as the nation's top law enforcement official to lead the Justice Department—has repeatedly violated his oath of office in a way that has put the interests of the president ahead of those of the American people.

Common Cause president Karen Hobert Flynn, who authored and signed the letter, said the Attorney General "has politicized the Department of Justice and undermined trust in the law by prioritizing and acting in the interests of a president who has committed impeachable offenses, rather than upholding the law and the Constitution."

Barr, she added, "has repeatedly violated his oath to the people he swore to protect and must be impeached and removed from office. The American people deserve an Attorney General committed to upholding the Constitution and applying the law without fear or favor. The Attorney General has repeatedly proven unwilling to put the interests of the nation before those of the man who appointed him and he must be removed from office before he does more harm to the nation."

Time and time again, Attorney General William Barr has misled the public and Congress in an attempt to protect President Trump’s lawless behavior. Read my letter to Congress on behalf of @CommonCause on why he must be impeached and removed from office.https://t.co/BMqDIHpTck pic.twitter.com/YiJF4ZOWAR — Karen Hobert Flynn (@KHobertFlynn) December 17, 2019

The 9-page letter lays out the case for impeaching Barr in detail. According to a statement from the group:

Most recently Barr ignored the evidence and conclusions of the Justice Department Inspector General's report finding the FBI properly launched an investigation of Russian interference in the 2016 election. Previously the Attorney General mischaracterized and undermined the work and conclusions of Special Counsel Robert Mueller into Russian election interference and obstruction of justice – intentionally delaying the release of the actual report in order to release his own "summary" to undercut the Special Counsel’s findings. The letter also details Barr's actions to facilitate the Trump Administration’s unlawful withholding of the Ukraine whistleblower complaint from Congress on the basis of his Office of Legal Counsel’s severely flawed reasoning—reasoning sharply criticized by the DOJ’s own Inspector General and dozens of other federal agency inspectors general. Further the letter outlines the Attorney General’s obstruction of the congressional investigations into the Trump Administration’s attempt to insert a citizenship question into the 2020 Census by continuing to defy lawfully-issued Congressional subpoenas.

Paul S. Ryan, Common Cause vice president for policy and litigation, said, "Barr is blatantly abusing the considerable powers of his office and undermining the rule of law in this nation and he must be removed from office."

Ryan characterized Barr's abuse of power as "unprecedented for an Attorney General of the United States and cannot be tolerated in a democracy," and said, "Congress must move swiftly to impeach and remove William Barr from office."

Common Cause is not the first to call for Barr's removal. In April, the progressive advocacy group CREDO Action also called for the Attorney General to be impeached, accusing Barr of covering up for Trump in the wake of Special Counsel Robert Mueller's report.

This fall, as the focus of Trump's misconduct shifted to his efforts to pressure the Ukrainian government to dig up dirt on his 2020 Democratic rival Joe Biden, Barr's efforts to use his position at the DOJ to insulate the president from accountability spurred fresh calls for the Attorney General's ouster.

"This isn't a presidential administration, it's a criminal enterprise," tweeted 2020 Democratic presidential candidate Julián Castro in early October. "The evidence is clear: both Trump and Barr must be impeached."