Sen. Lindsey Graham (R-S.C.) says the Senate needs to investigate President Trump’s decision to end his former national security adviser John Bolton’s personal security protection.

Bolton, who clashed with Trump at the end of his first term, had been under Secret Service protection because of a threat on his life from Iran.

Graham, during an interview with CNN’s “State of the Union,” argued the U.S. government can’t leave former national security officials “hanging” after they’ve confronted one of the nation’s adversaries, such as Iran.

And he said the Senate needs to get involved and figure out why Bolton and Trump’s former Secretary of State Mike Pompeo lost their personal security details.

“Whether you like Bolton or anybody else, we need to make sure that if you serve in our government and you take a foreign power at the request of the administration, that we do not leave you hanging,” Graham told CNN’s Dana Bash.

“The Senate needs to look at what happened and sit down and figure out what’s the best way forward,” he said.

He said Senate Intelligence Committee Chair Tom Cotton (R-Ark.) told him that the threat against Bolton and other former national security officials “seemed to be real.”

“And I don’t want to leave them hanging. It makes it hard to recruit people in the future,” he said.

Graham warned that Trump needs to think of the potential consequences if one of the officials who lost their personal security protection were to get seriously injured or killed by an assassin.

“And, you know, if something happened to these people and, you know, President Trump needs to think about, you know, getting people to serve in the future. Owning that decision,” he said.