Attorney General Jeff Sessions resigned from his position in the Department of Justice Wednesday afternoon, one day after voters went to the polls in the midterm elections.

In a letter addressed to President Donald Trump, Sessions wrote: “At your request, I am submitting my resignation.” He went on to tout the department’s record under his leadership and said he “had no greater honor than to serve alongside” law enforcement officers.

Session’s resignation was not surprising, as the president previously signaled there would be changes to his administration after the midterms. Sessions, once among the president’s most loyal supporters, drew Trump's scorn after his recusal from the Russia probe.

For more than a year, Trump repeatedly criticized Sessions, saying he wouldn’t have selected Sessions for the attorney general role if he’d known Sessions would ultimately recuse himself from Special Counsel Robert Mueller's investigation.

Trump on Wednesday tweeted that Matthew G. Whitaker, Chief of Staff to Attorney General Jeff Sessions at the Department of Justice, "will become our new Acting Attorney General of the United States."

"We thank Attorney General Jeff Sessions for his service, and wish him well! A permanent replacement will be nominated at a later date," he added.

The resignation drew sharp reactions from lawmakers on both sides of the aisle.

California Democratic Rep. Nancy Pelosi accused Trump of using Sessions' resignation as a means to threaten Mueller's Russia probe.

"It is impossible to read Attorney General Sessions’ firing as anything other than another blatant attempt by @realDonaldTrump to undermine & end Special Counsel Mueller’s investigation," she tweeted. "Given his record of threats to undermine & weaken the Russia investigation, Matthew Whitaker should recuse himself from any involvement in Mueller’s investigation. Congress must take immediate action to protect the rule of law and integrity of the investigation. #FollowTheFacts"

Senate Minority Leader Chuck Schumer commented on Sessions while holding a news conference about the midterm elections, saying he felt the announcement was suspicious.

“I’m not going to say much until I read what they said and why. I find the timing very suspect, number one. But number two, our paramount view is that any attorney general, whether this one or another one, should not be able to interfere with the Mueller investigation in any way," Schumer said. "They should not be able to end it, they should not be able to limit it, they should not be able to interfere with Mueller going forward and doing what he thinks is the right thing."

In a later statement, Schumer similarly called for Whitaker to recuse himself.

“Given his previous comments advocating defunding and imposing limitations on the Mueller investigation, Mr. Whitaker should recuse himself from its oversight for the duration of his time as acting attorney general," Schumer said.

Former Attorney General Eric Holder said on Twitter he worries Session's exit could negatively impact Mueller's investigation, adding "this is a red line."

"Anyone who attempts to interfere with or obstruct the Mueller inquiry must be held accountable," Holder tweeted. "We are a nation of laws and norms not subject to the self-interested actions of one man."

Senate Majority Leader Mitch McConnell released a statement praising Sessions for “dedicated service” in his role as the nation’s top law enforcement officer.

“Throughout his career, as a prosecutor, a Senator and as Attorney General, he remained steadfast in his commitment to the rule of law and his love of our great nation,” McConnell’s statement said. “I wish him well and look forward to working with him in any future endeavors.”

Sen. Chuck Grassley called Sessions “a true public servant” on Twitter.

“Thx to AG Jeff Sessions for his service to our country both leading the DOJ & in the US Senate serving the ppl of Alabama I‘ve enjoyed working with him for decades,” the tweet said.

Democratic Rep. Adam Schiff of California slammed Trump on Twitter for desiring "an Attorney General to serve his interest, not the public."

"Mueller's investigation and the independence of the DOJ must be protected," Schiff said. "Whitaker and any nominee must commit to doing both. We will protect the rule of law."

Republican South Carolina Sen. Lindsey Graham in a statement said Session's carried out his duties as attorney general "honorably" and that he "dedicated his whole life to conservatism and upholding the Rule of Law."

“I look forward to working with President Trump to find a confirmable, worthy successor so that we can start a new chapter at the Department of Justice and deal with both the opportunities and challenges our nation faces," Graham continued.

House Democratic Whip Steny H. Hoyer, D-Md., said the country had a right to know the details behind Sessions' resignation.

“The American people deserve to know why President Trump asked for the resignation of Attorney General Sessions," Hoyer's statement said. "If the firing of Attorney General Sessions is President Trump’s opening move to undermine, meddle in, or terminate Special Counsel Robert Mueller’s investigation into Russian interference in the 2016 presidential election and related matters, the President must be held accountable. Congress must take bipartisan action to protect the integrity of Special Counsel Mueller’s investigation.”

Sen. John Cornyn, R-Texas, released a statement, praising Sessions for his decades-long dedication to public service.

“Attorney General Sessions has selflessly dedicated more than 40 years to serving the people of Alabama and the nation,” Cornyn said in a statement. “As our country’s top law enforcement official, he has been integral in fighting the opioid epidemic, keeping violent criminals off our streets, and supporting victims. Those who know him understand his commitment to the rule of law, and his deep and abiding concern for our country.”

Connecticut Democratic Sen. Richard Blumenthal said Sessions' resignation was "a break the glass moment" and slammed the president for his choice in who would temporarily fill the role.

“Replacing the Attorney General with a non-Senate-confirmed political staffer is highly irregular and unacceptable," Blumenthal said. "Protecting the Special Counsel investigation is more urgent than ever. My Republican colleagues must rise to the challenge and show political backbone by demanding that Mr. Whitaker recuse himself from oversight of the Special Counsel’s investigation."

Republican Sen. Mike Lee of Utah released a statement, describing Sessions as "a dear friend who has served our nation admirably."

Sen. Mark Warner, D-Va., in a statement, said that Sessions' resignation cannot be used as a catalyst to interfere in the Russia investigation and characterized a potential attempt as "a gross abuse of power by the President."

“While the President may have the authority to replace the Attorney General, this must not be the first step in an attempt to impede, obstruct or end the Mueller investigation," Warner said.

The American Civil Liberties Union (ACLU) executive director Anthony D. Romero, on the other hand, issued a statement condemning Sessions as “the worst attorney general in modern American history.”

“He was an egregious violator of civil rights and civil liberties. From his plot to deport Dreamers, remove police and law enforcement accountability, discriminate against trans people, perpetuate and expand senseless enforcement of racist drug laws, use of religion to discriminate against LGBTQ people and undermine reproductive rights, abandon protections for women against violence, and even lie to the Senate to cover up Trump campaign contact with Russian officials, his tenure as the highest chief law enforcement officer was a complete disgrace to our nation’s constitutional protections,” Romero wrote. “Sessions allowed the Department of Justice to function as the political arm of the Trump administration to undo fundamental rights that protect each of us, disregarding years of legal precedent and settled law.”

He vowed to maintain “a close watch” on Mueller’s investigation going forward “and the impact of the appointment of a new Attorney General.”

Fox News' Alex Pappas and Jake Gibson to this report.