(CNN) Republican Sen. Chuck Grassley of Iowa told CNN on Monday he will "try to get to the bottom" of what happened with the firing last week of State Department Inspector General Steve Linick, saying that "it's not difficult for me to take on any President."
"That's my reputation, Republican or Democrat," Grassley told CNN, a reference to his long-held stance defending government oversight and protecting whistleblowers at government agencies.
Asked if he was concerned about the pattern of President Donald Trump firing four inspector generals in recent weeks, Grassley responded: "Whether you have a Democratic president or a Republican president, I see my job of oversight Article I versus Article II."
Grassley sent a letter to Trump earlier Monday asking for an explanation for his firing of Linick. Grassley had also sent a similar letter after former Intelligence Community Inspector General Michael Atkinson's dismissal last month.
"I want to work with you to ensure that the enemy here is wasteful government spending, not the government watchdogs charged with protecting the taxpayer," Grassley wrote. "To that end, please provide a detailed reasoning for the removal of Inspector General Linick no later than June 1, 2020. Please also provide me and my colleagues a written response to our letter of April 8, 2020, regarding the removal of Inspector General Atkinson as soon as possible."
Grassley's request for information comes as senior Republicans on Capitol Hill have remained mostly silent since Trump announced Friday that he would fire the State Department watch dog, who was investigating Secretary of State Mike Pompeo.
GOP Sen. Mitt Romney, though, called it a "threat to accountable democracy." And several other Republicans have also requested more information on the circumstances behind the ousting.
Grassley, the chamber's most senior Republican, has been a long-time defender of whistleblowers and government oversight and has broken with Trump on the topic several times during his presidency.