As the investigation into Russian interference in the 2016 presidential election – and any involvement from the Trump campaign – forges ahead, Deputy Attorney General Rod Rosenstein found himself on the receiving end of some Republicans’ ire.

Special Counsel Robert Mueller is spearheading the Russia probe, but Rosenstein, 53, still oversees the federal investigation as deputy attorney general. But Rosenstein plans to leave his post in the coming weeks as a new attorney general is confirmed, sources told Fox News.

Read on for a look at how Rosenstein is connected to the Russia investigation.

What was Rosenstein’s job?

Rosenstein was confirmed by the Senate as deputy attorney general in April 2017.

As deputy attorney general, he is responsible for day-to-day operations of the Justice Department and oversees its agencies, including the FBI.

How is he involved in the Russia investigation?

Rosenstein appointed Mueller as the special counsel to oversee the investigation into Russian influence in the 2016 election in May 2017. The appointment came after then-Attorney General Jeff Sessions recused himself from the probe, and Rosenstein stepped in to oversee the investigation. At the time, Rosenstein said his decision to appoint a special counsel was “not a finding that crimes have been committed or that any prosecution is warranted.”

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The appointment came after then-Attorney General Jeff Sessions recused himself from the probe, and Rosenstein stepped in to oversee the investigation. At the time, Rosenstein said his decision to appoint a special counsel was “not a finding that crimes have been committed or that any prosecution is warranted.”

Under Justice Department regulations, Mueller must consult with Rosenstein when his investigators uncover new evidence that may fall outside his original mandate. Rosenstein then determines whether to allow Mueller to proceed or to assign the matter to another U.S. attorney or part of Justice.

According to a memo from Republicans on the House Intelligence Committee, Rosenstein signed at least one FISA surveillance application that targeted Carter Page, a former foreign policy adviser on Trump’s campaign.

Did he have something to do with Comey’s firing?

Democrats were critical of Rosenstein after the White House used a memo he'd crafted as a reason to fire FBI Director James Comey in May 2017. Rosenstein reportedly drafted the memo after Trump had expressed his desire to fire Comey.

Rosenstein later told lawmakers he stood by his memo. He said it was “not a finding of official misconduct” or “a statement of reasons to justify a for-cause termination.”

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"Notwithstanding my personal affection for Director Comey, I thought it was appropriate to seek a new leader,” Rosenstein said.

What has the White House said about him?

As he has continued to deny any wrongdoing, Trump has been critical of the Russia investigation, particularly of Mueller’s handling of it.

In an April tweet, Trump accused Mueller of being “conflicted” – and Rosenstein even more so.

Fox News' Samuel Chamberlain, Gregg Re, Brooke Singman and The Associated Press contributed to this report.