Lawmakers are raising separation-of-powers concerns as the White House seeks to install a Justice Department official at the legislative-branch institution.

The president named Todd Blanche, the deputy attorney general, as the acting librarian. But staff members refused access to two department officials he chose for key roles at Congress’s main research arm.

Trump has fired Carla Hayden, the longtime head of the Library of Congress, a move Democrats panned as “callous” and “ignorant.”