Trump signaled late Friday he intends to nominate Army Secretary Mark Esper to permanently fill the role. But Esper, who is set to take over as acting Defense head on Monday, will still need his nomination formally submitted to the Senate.

Lawmakers argue that growing tensions with Iran and looming funding negotiations — where lawmakers will need to agree to raise the caps on defense spending — require Trump to move quickly to get a Senate-confirmed official in place at the Pentagon.

"We need a permanent secretary of Defense to help guide the department through budget negotiations and conflict," he said, adding, "I would encourage the president to find somebody quickly to ascend to the Senate."

Asked about the shake-up at the Pentagon amid escalating concerns about a military conflict with Iran, with Trump on Friday confirming that the administration had been considering strikes, Graham replied, “Yeah, that’s why we need somebody permanent.”

The White House is known for letting nominations languish for weeks before formally submitting them, a dynamic that has sometimes frustrated GOP senators. Shanahan's nomination, for example, was announced in early May, but when he withdrew this week, his paperwork still hadn't been sent to Capitol Hill.

Shanahan’s decision to withdraw from consideration caught GOP senators off guard , with several suggesting they were learning only through news reports the details of past domestic violence incidents involving his family.

Pushing forward with the nomination would have set the stage for a brutal confirmation fight, keeping the reports about Shanahan's family in the spotlight with no guarantee he could have recovered and ultimately been confirmed.