A day earlier, Mr. Rooney became the first House Republican to indicate that he was willing to consider supporting articles of impeachment over the president’s attempts to pressure Ukraine to investigate his political rivals, but he said on Saturday that his decision to retire was unrelated. (He emphasized to reporters that the allegations did not rise to the level of the Watergate scandal.)

“I’m going to do at all stages what I think is right to do,” Mr. Rooney told reporters on Friday when asked if he was more outspoken because he was considering retirement. “You’ve got to do the right thing at every stage. Whether I run again is a totally different can of worms, that has to do with family things, business, wanting to do some different things.”

“This is kind of a frustrating job for me,” he added. “I come from a world of actions, decisions, putting your money down and seeing what happens. This is a world of talk.”

As a member of the House Foreign Affairs Committee, Mr. Rooney has had access to the closed-door interviews conducted during the open impeachment inquiry, which has brought a parade of career diplomats and senior officials to the Capitol to give hourslong testimony. A former ambassador to the Holy See, he defended the career diplomats who have testified, telling reporters on Friday that “it’s painful to me to see this kind of amateur diplomacy, riding roughshod over our State Department apparatus.”

He also offered some of the bluntest criticism of a top White House official’s efforts to walk back earlier statements saying that Mr. Trump had sought a quid pro quo in withholding American aid from Ukraine.