He was joined 24 hours later by Isakson, who had been absent from Capitol Hill all week contending with back pain.

“After careful consideration, Senator Isakson has decided that he will join his Senate colleagues in co-sponsoring the McConnell-Graham resolution,” spokeswoman Amanda Maddox said. “He has said all along that he wants to make sure he’s doing his part as a member of the Senate to ensure a fair process.”

The resolution comes as Georgia Republicans and the congressional GOP more broadly have upped their defense against the probe at the urging of the president.

The investigation, which House Speaker Nancy Pelosi announced last month, has divided the Georgia delegation along party lines, although some local Democrats have stopped short of endorsing outright impeachment at this point in the process. The opinions on both sides have only appeared to harden in the weeks since.

“I do not believe that the president is above the law,” U.S. Rep. Sanford Bishop, a centrist Democrat from Albany, told The Atlanta Journal-Constitution on Tuesday. The “separation of powers enumerated in the Constitution … has to be upheld and protected if our democracy is to survive.”

Local Republicans have zeroed in on the process surrounding the proceedings rather than the substance of the allegations themselves. In addition to the closed-door nature of recent hearings, they’ve highlighted House Intelligence Committee Chairman Adam Schiff’s dramatization of Trump’s phone call with his Ukrainian counterpart and Pelosi’s refusal to schedule a vote in the full House to launch the probe as Congress did during past impeachment debates.

The president praised the roughly two-dozen House Republicans who flooded a secure hearing room on Capitol Hill on Wednesday as the deposition of a senior defense official was about to occur, delaying her testimony by five hours. The group of lawmakers, which included three Georgians — U.S. Reps. Buddy Carter of Pooler, Jody Hice of Monroe and Rick Allen of Evans — said Democrats were eschewing transparency by holding hearings behind closed doors. (Hice, as a member of the House Oversight Committee, has been able to participate in the inquiry while it’s being conducted behind closed doors.)

“This is not the Soviet Union. This is the United States of America,” Carter said Wednesday.

U.S. Rep. Hank Johnson, a Democrat from Lithonia, said in a tweet that he agreed with a House colleague who characterized the Republicans’ action as “really shameful behavior.”

Johnson is a member of the House Judiciary Committee, which traditionally has jurisdiction over impeachment matters.

Democrats deny that Republicans are being treated unfairly, noting they have had equal time to question witnesses and full access to the meetings. Schiff says closed-door hearings are necessary to prevent witnesses from concealing the truth, and he has promised to release the transcripts when it will not affect the investigation.

Across the Capitol, Perdue called the probe “nothing but a political partisan show trial to keep obstructing this president.”

“It’s time to have a formal inquiry and take it out of the backrooms of the House so the people of America can see just how ridiculous this is,” he said Tuesday as Bill Taylor, the acting U.S. ambassador to Ukraine, delivered explosive testimony disputing Trump’s claim that there were no “quid pro quo” with Ukraine.

Isakson has generally declined to opine about the Democratic probe, citing his role as a potential juror in a Senate impeachment trial. Still unclear is whether the House will vote on impeachment articles before the end of the year, when Isakson is set to step down because of health reasons.

“He will continue to carefully monitor all the information available should the matter come before the Senate for consideration before his retirement on Dec. 31,” Maddox said of Isakson.

The Senate GOP’s resolution needs 51 votes to pass, which means every Senate Republican will be under extreme pressure to lend their support.

That pressure is also coming from the outside. Debbie Dooley, a co-founder of the Atlanta Tea Party Patriots, called the impeachment process “illegitimate” in a post on Twitter this week and said Senate Republicans need to stop the proceedings “or face the ire of the GOP base.”

Staff writer Jim Galloway contributed to this article.

BALANCED COVERAGE

The debate over impeachment is divisive, and these types of controversial stories receive special treatment. We always try to present as much information as possible so that readers can reach their own conclusions. To do that, we present multiple points of view. Today’s story, for example, contains comments from Georgia’s two Republican senators and responses from House Democrats.