The Senate voted 54-37 on Sunday to advance Markwayne Mullin's nomination to lead the Department of Homeland Security. Why it matters: Mullin is on track to be confirmed this week to succeed Kristi Noem as Homeland Security secretary when Noem steps down at the end of the month. Mullin, a first-term senator, won approval from the Homeland Security and Governmental Affairs Committee on Thursday in a narrow, 8-7 vote , despite opposition from the panel's chairman, Rand Paul (R-Ky.). Editor's note: This is a developing story. Please check back for updates.