Senator Markwayne Mullin of Oklahoma will testify before the Senate Homeland Security Committee on Wednesday as President Trump's nominee to lead the Department of Homeland Security. Mullin, who replaced the ousted Kristi Noem, faces questions about carrying out Trump's mass deportation campaign and reforming an agency roiled by controversies.

Mullin's confirmation comes amid a tumultuous period for DHS, with funding lapsed for over a month and roughly 100,000 employees working without pay. Democrats have refused to pass a spending bill without new restrictions on immigration enforcement, including barring agents from wearing masks. The department has faced intense scrutiny after immigration officers fatally shot two U.S. citizens in Minneapolis.

While Mullin enjoys strong support among Republicans and is personally well-liked by colleagues across party lines, he could face sharp questioning from both Democrats and Senator Rand Paul, the committee chairman. Democrats plan to press Mullin on his immigration enforcement stances and demand commitments for policy changes. His financial dealings, including extensive stock trading since entering Congress in 2013, may also come under scrutiny.