President Obama’s nominee for Homeland Security inspector general is scheduled to testify before a Senate panel Wednesday, bringing the administration one step closer to filling a role that has remained vacant for nearly three years.

John Roth, who has led the Food and Drug Administration’s criminal investigations office since last year, would replace former acting Homeland Security inspector general Charles Edwards, who stepped down amid allegations of nepotism and abuse of power.

Edwards resigned in December amid a Senate investigation but he has denied the claims against him, calling them “false allegations” and “personal attacks.”

If confirmed, Roth would be in charge of an investigation into allegations against Alejandro Mayorkas, the newly confirmed No. 2 at Homeland Security and former U.S. immigration director who is accused of helping secure worker visas on behalf of a firm tied to Virginia Gov.-elect Terry McAuliffe (D) and Anthony Rodham, a brother of Hillary Rodham Clinton.

Obama has struggled to fill many of the key positions at the Department of Homeland Security, which is home to the third-largest executive-branch workforce, including agencies such as Customs and Border Protection, the Coast Guard, the Transportation Security Administration and the Federal Emergency Management Agency. About 40 percent of the top roles are either unfilled or held by acting officials.

The department’s leadership ratings were lowest among large agencies in the 2013 “Best Places to Work in the Federal Government” report, which is based on the government’s annual employee-viewpoints survey. Its senior-leadership score was particularly bad, with 35 points out of 100. DHS also ranked last in its category with an overall score of 46.8 points.

In recent months, Obama has made progress in choosing nominees for some of the Homeland Security leadership openings, and new Senate rules prevent Republicans from filibustering to block votes on those picks as they have done in the past.

With the new guidelines in place, the Senate last month confirmed Jeh Johnson, former general counsel for the Pentagon, to serve as secretary of homeland security. In a party-line vote that month, the Senate also confirmed Mayorkas.

Senate lawmakers have showed little resistance to Roth’s nomination, but members of both parties have said he’ll face challenges if confirmed.

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