Representative Mark Amodei of Nevada on Friday became the first Republican member of the House of Representatives to back the rapidly escalating impeachment inquiry — but he said he was reserving judgment on whether President Trump should be impeached.
Mr. Amodei, 61, a four-term congressman from Carson City, is the chairman of Trump’s re-election campaign in Nevada, a swing state that the president lost by 27,000 votes to Hillary Clinton in 2016.
He said it made sense for Congress to investigate a whistle-blower’s complaint, made public on Thursday, that Mr. Trump used a July 25 phone call with Ukraine’s president to advance his personal interests, including asking him to look into unsubstantiated allegations of corruption against former Vice President Joseph R. Biden Jr. and his younger son.
Mr. Amodei discussed the impeachment inquiry process during a conference call on Friday with members of the news media from his home state, and in a follow-up statement issued by his office.
“Listen, I want to see what the process produces,” Mr. Amodei said on the conference call, explaining that he had not ruled out impeachment. “And quite frankly, if there’s something there that rises to that level, then guess what, that’s not something that we can have by a Democrat or a Republican.”
A majority of House members now support the impeachment inquiry into Mr. Trump, according to a New York Times survey and public statements. On Tuesday, Nancy Pelosi, Democrat of California and the House speaker, announced that the House would begin such an inquiry.
Justin Amash, independent of Michigan and a former Republican, had publicly favored impeachment even before the whistle-blower’s complaint. Other than Mr. Amash, Mr. Amodei is the only non-Democrat in the House who backs the inquiry.
Jim Himes, Democrat of Connecticut and second highest-ranking member of his party on the House Intelligence Committee, said Friday night that Mr. Amodei’s support for the inquiry was significant.
“That’s a big deal,” Mr. Himes said in a phone interview, adding that the transcript of the call between Mr. Trump and Ukraine’s president, Volodymyr Zelensky, was damning. “That transcript — this is mob stuff.”
He said Mr. Amodei’s position was similar to the stance of many Democrats, including Mr. Himes, who support the inquiry but have stopped short of backing impeachment. He said that Democrats had not predetermined Mr. Trump’s fate.
A spokesman for Kevin McCarthy, Republican of California and the House G.O.P. leader, did not immediately respond to a request for comment on Friday night.
Mr. Amodei, a former federal prosecutor, said that he was a big fan of oversight and that Congress should let the chips fall where they might.
“Please, nobody hang up the phone and say, ‘Amodei is Pelosi’s defender,’ ” he said on the conference call.