Sen. Markwayne Mullin (R-Okla.) is poised to be the next Homeland Security Secretary, replacing Kristi Noem, President Trump announced Thursday.Why it matters: Mullin is a staunchly MAGA firebrand and will likely be in lockstep with Trump's immigration agenda.What they're saying: "Markwayne will work tirelessly to Keep our Border Secure, Stop Migrant Crime, Murderers, and other Criminals from illegally entering our Country, End the Scourge of Illegal Drugs and, MAKE AMERICA SAFE AGAIN," Trump sa...