(CNN)Attorney General Merrick Garland is testifying before the Senate Judiciary Committee on Wednesday, where he is likely to face fierce Republican blowback to a memo he issued addressing threats to school boards, as well as bipartisan heat for the FBI's handling of the Larry Nassar probe.

       Garland's appearance comes as the Justice Department weighs whether to prosecute Steve Bannon -- a close ally of former President Donald Trump -- after the House voted to hold him in contempt for not cooperating in its January 6 investigation.

       In a scathing prepared opening statement obtained by CNN, Sen. Chuck Grassley of Iowa, the top Republican on the Judiciary Committee, will claim that President Joe Biden has "politicized" department decision-making in telling reporters the department should prosecute witnesses who defy subpoenas in the House probe. Biden said last week at a CNN town hall that he had been wrong to make that statement.

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       In addition to the House investigation, the Senate Judiciary Committee has undertaken its own review of how Trump sought to use the Justice Department in his efforts to overturn his 2020 electoral defeat. The Justice Department, in consultation with the White House, has allowed former officials at the department to participate in the investigation. Garland will likely tout at Wednesday's hearing the federal investigation into the violent attack on the Capitol, which has led to the arrest of more than 600 individuals.

       Republicans, for their part, have had their attention on non-January 6 issues. At a House Judiciary Committee hearing with Garland last week, the Republicans zeroed in on a controversial school board memo that instructed the FBI to take certain steps to work with local and state law enforcement responding to harassment and threats targeting school officials.

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       Republicans have equated the Justice Department's approach with treating parents like "domestic terrorists" for protesting schools' Covid protocols and methods of teaching about race in American history. (The memo makes no reference to domestic terrorism.) Sen. Josh Hawley, a Missouri Republican and a member of the Judiciary panel, has called on Garland to resign over the memo.

       According to his prepared remarks, Grassley will say, "The last thing the Justice Department and FBI need is a vague memo to unleash their power—especially when they've shown zero interest in holding their own accountable."

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       Republicans have sought to make the memo a prominent issue in the tight Virginia gubernatorial race, where Republican Glenn Youngkin released a campaign ad claiming that the FBI was trying to "silence parents."

       While Democrats have defended Garland's memo, they have been less pleased with the department's response to the FBI's mishandling of the Nassar probe, with delays that allowed at least 70 gymnasts to be abused after the FBI first learned of the misconduct, according to a recent DOJ inspector general report.

       The department has attracted bipartisan scorn for its decision not to prosecute two former FBI officials accused of making false statements in the fallout from the botched probe.

       Additionally, Garland may face questions from Democrats about voting rights and the DOJ's actions on police reform. Republicans, meanwhile, could grill Garland on the status of special counsel John Durham's review of the launch of FBI's Trump-Russia probe in 2016.

       CNN's Jeremy Herb contributed to this report.