The final vote sailed through the Senate, but it wasn't always smooth sailing for Shanahan on Capitol Hill.
He was excoriated during his confirmation hearing
last month by Sen. John McCain, the chairman of the Senate Armed Services Committee. McCain slammed Shanahan for a written answer on his questionnaire to the committee about providing weapons to Ukraine, and the Arizona Republican threatened to block Shanahan's confirmation if he didn't provide a better response.
"Inexplicably, you responded by saying you'd have to look at the issue," McCain said at Tuesday's hearing. "Not a good beginning. Do not do that again, Mr. Shanahan, or I will not take your name up for a vote before this committee. Am I perfectly clear?"
"Very clear," Shanahan responded.
A week later, Shanahan provided 10 pages of "revised" answers
to the committee's policy question, in which he stated that he supported providing lethal weapons to Ukraine.
His response was enough for McCain, and that cleared the way for his nomination to get through the Senate.
But McCain's missive during the confirmation hearing is a sign that Shanahan still could face trouble on the Hill.
In addition to the Ukraine answer, McCain singled out Shanahan as a Boeing executive, saying he was weary of top officials from the "big five" defense contractors -- Boeing, Lockheed Martin, Northrop Grumman, General Dynamics and Raytheon -- taking senior Pentagon jobs.
McCain, who is not in the Senate this week while he recovers from surgery
to remove a blood clot above his left eye, has a history of clashing with Boeing, and he often rails against the "defense-industrial-congressional complex."
"I want to give the secretary of defense the team he needs, but I'm not going to give him a team that I think is business as usual over the last eight years," McCain said.
Shanahan will succeed Bob Work, who was President Barack Obama's deputy defense secretary and stayed in the role in the opening months of the Trump administration. Work's last official day was Friday.