On Wednesday morning, President Donald Trump appointed Robert O’Brien as his new national security adviser. The appointment follows last week’s departure of former national security adviser John Bolton. O’Brien was formerly the State Department’s chief hostage negotiator.

Homeland Security expert Juliette Kayyem joined Boston Public Radio on Wednesday, and said Trump’s choice signals a growing influence from Secretary of State Mike Pompeo.

“[O’Brien] is low on the totem pole of responsibilities he’s had in the past when you think of … Michael Flynn, a general; HR McMaster, a well-known general; John Bolton, a well-known intellectual and former government official,” Kayyem said. She added, “You’re now at a very different level. … I think [O’Brien] got picked because he’s Mike Pompeo’s guy.”

Kayyem credited Pompeo as “politically savvy,” with larger political ambitions than his current role in the Trump administration.

“I think Mike Pompeo has a clear sense that his pathway to the presidency is through Trump,” she said. “He will not be McMaster, Tillerson, Maddis. His exit from the Trump administration will be on his own terms.”

Kayyem is an analyst for CNN, former assistant secretary at the Department of Homeland Security and faculty chair of the homeland security program at Harvard University’s Kennedy School of Government.