WASHINGTON — Republican senators are lost and adrift as the impeachment inquiry enters its second month, navigating the threat to President Donald Trump largely in the dark, frustrated by the absence of a credible case to defend his conduct and anxious about the historic reckoning that likely awaits them.

Recent days have delivered the most damaging testimony yet about Trump and his advisers commandeering Ukraine policy for the president’s personal political goals, which his allies on Capitol Hill sought to undermine by storming the deposition room and condemning the inquiry as secretive and corrupt.

Those theatrics belie the deepening unease many Republicans now say they feel — particularly those in the Senate who are dreading having to weigh their conscience against their political calculations in deciding whether to convict or acquit Trump should the Democratic-controlled House impeach the president.

In hushed conversations over the past week, GOP senators lamented that the fast-expanding probe is fraying their party, which remains completely in Trump’s grip. They voiced exasperation at the expectation that they defend the president against the troublesome picture that has been painted, with neither convincing arguments from the White House nor confidence that something worse won’t soon be discovered.

“It feels like a horror movie,” said one veteran Republican senator, who spoke on the condition of anonymity to candidly describe the consensus.

The Republican Party’s strategy is being directed almost entirely by the frenzied impulses of Trump, who has exhibited fits of rage over the Democrats’ drive to remove him from office for abuse of power.

“I did nothing wrong,” Trump told reporters Friday. “This is a takedown of the Republican Party.”

Although Sen. Mitt Romney, R-Utah, has been a loud dissenter, he has been speaking for himself as opposed to acting as a frontman for some silent caucus of like-minded Republicans, according to people familiar with the dynamic. Most GOP senators have been taking cues from Majority Leader Mitch McConnell, R-Ky., whose paramount concern has been maintaining his party’s control of the chamber in next year’s election.

“They’ve decided that they’re going to take it all grudgingly — and privately, perhaps, in disgust — but they’re not going to give up the farm,” said Al Cardenas, former chairman of the American Conservative Union. But, he added, “It’s been piling on, piling on, piling on, and I see defense fatigue on behalf of the Republicans in the Congress.”

The GOP majority is in play in 2020, with Sens. Susan Collins of Maine, Joni Ernst of Iowa, Cory Gardner of Colorado, Martha McSally of Arizona and Thom Tillis of North Carolina each facing tough campaigns and grappling with polls in their states showing independent voters souring on Trump and open to impeachment.

“At some point, McConnell is going to have to perform triage to save the majority,” said Rick Wilson, a longtime GOP consultant and Trump critic. “How the Senate Republicans handle everything is all going to come down to how threatened Mitch feels and how worried he is about losing Colorado, North Carolina and a few others states. And if Trump’s numbers keep dropping, that decision is going to come sooner than later for him.”

Trump and his allies have strained to focus the debate on the process, but Republican officials have struggled to answer for the substance of the startling statements made by the growing list of credible witnesses from the national security and diplomatic realms.

“There’s frustration. It feels to everyone like they’re just digging a hole and making it worse. It just never ends. … It’s a total (expletive) show,” said one Republican strategist who has been advising a number of top senators and who, like several others interviewed, spoke on the condition of anonymity to be candid.

McConnell, who has shared related concerns in private conversations with other senators, has been preparing for a possible Senate impeachment trial. And earlier this month he showed a dry PowerPoint presentation to Republican senators explaining how one might unfold.

McConnell remains engaged with Trump but has a mixed view of the president’s advisers, several Republicans said, noting that he misses his productive working relationship with former White House counsel Donald McGahn and is “less enamored” with his successor, Pat Cipollone, according to a McConnell ally. A Senate GOP aide said McConnell and Cipollone have a good working relationship.

As they went about their work at the Capitol this past week, many Senate Republicans were all but mute when reporters asked questions about impeachment — a stark snapshot of a party rattled not only by the House inquiry but also by Trump’s removal of U.S. troops from northern Syria; his decision, later retracted, to host next year’s Group of Seven summit at his Florida golf resort; and his claim that the investigation into him amounted to a “lynching.”

“I’m a juror and I’m comfortable not speaking,” Sen. James Risch, R-Idaho, said. Pressed again for comment, he reiterated, “I said I’m comfortable not speaking.”

“I’d be a juror, so I have no comment,” Sen. Lamar Alexander, R-Tenn., said.

“I don’t need a strategy for impeachment because I may be a juror someday,” Sen. Tim Scott, R-S.C., said.

Even as they withheld judgment of Trump’s conduct, Republican senators were quick to try to exploit vulnerabilities in the process being run by House Speaker Nancy Pelosi, D-Calif., and House Intelligence Committee Chairman Adam Schiff, D-Calif.

“To be honest, I don’t follow any of it because that’s not due process,” Sen. Dan Sullivan, R-Alaska, said. “Secret hearings, selective leaks. And that’s due process? In my America, that’s not due process.”

For Republicans, the political conundrum is a problem of their own making, argued William Galston, a senior fellow in governance at the Brookings Institution. “They normalized a president whose conduct they are now being asked to judge as so abnormal as to warrant his removal from office,” he said.

“To the extent that they quietly harbor conscientious objections to what the president is doing — or, even more spectacularly, how he’s doing it — they have to weigh the calling of conscience against political considerations,” Galston added. “There’s a reason why ‘Profiles in Courage’ is a very short book. Courage is not the norm. It’s the exception.”

Trump was buoyed last week by a resolution introduced by Sen. Lindsey Graham, R-S.C., condemning the House’s impeachment inquiry as “illegitimate.” But eight Republican senators did not initially sign onto what Graham conceived of as a show of support for the president; five of them later did, leaving only Romney, Collins and Lisa Murkowski of Alaska as the holdouts.

Trump was given another lift in Republican enthusiasm Sunday when he announced that Abu Bakr al-Baghdadi, the elusive Islamic State leader, died during an American military operation in Syria. Top Republicans hailed the news as a significant victory in the fight against terrorism and praised Trump.

At the White House last week, counselor to the president Kellyanne Conway chided the media for what she characterized as a rush to judgment about Trump’s conduct. “Let’s take a deep breath and stop pretending we know what’s in somebody else’s heart, mind or soul, and just wait to see where the facts take us,” she told reporters.

Trump had lunch last Thursday with, among others, Alexander, who is retiring next year and is widely seen by his colleagues as driven by his personal integrity and therefore liable to vote against Trump if the case for his removal is strong, according to several lawmakers and GOP aides. Others in the camp of possible Republican breakaways — including Collins and Sen. Pat Toomey of Pennsylvania — have not engaged much with Trump or his advisers on impeachment, lawmakers and aides said.

Republicans have been grousing in private about the lack of a clear strategy at the White House and their limited grasp of the full set of facts and how officials are prepared to explain them.

“What’s causing the most pause is, what else is out there? What is around the corner?” said a second Republican strategist in regular contact with congressional leaders. “If they say something in defense of the president or against the impeachment inquiry now, will they be pouring cement around their ankles?”

White House acting chief of staff Mick Mulvaney, a former House member, has been a constant target of behind-the-scenes ire from GOP lawmakers. Talk about potential replacements for Mulvaney has become a parlor game on Capitol Hill, where Republicans have noted his inability to constrain Trump or build a political and messaging operation dedicated to countering the impeachment inquiry.

Rep. Mark Meadows, R-N.C., a conservative hard-liner, has been a fixture at the White House, talking to Trump “more than Mulvaney,” in the estimation of one Trump adviser who was not authorized to speak publicly. “Every time you look over toward the Oval, there is Mark Meadows,” this adviser said.

There are some signs that the White House is moving to do more to deal with the fraying among congressional Republicans, with Trump reaching out to more members by phone and discussions about bringing in a high-profile lawyer to deal directly with impeachment, as well as new communication aides.

The usual chorus of support for Trump from conservative media figures remains active but scattered. Former White House chief strategist Stephen K. Bannon has launched a podcast that he calls an outside “war room” for the president, broadcasting from the basement of his home on Capitol Hill. Meadows appeared on Bannon’s program last week, calling out House Democrats for “information warfare” and said it is “imperative that our team” counters with “real facts.”

But in the biggest blow yet to Trump, acting U.S. ambassador to Ukraine William B. Taylor Jr. testified last week that the president had personally intervened in a quid pro quo for U.S. military aid to be contingent upon Ukrainian investigations into Democrats. Some Republicans have tried to dismiss his account, arguing it is based on secondhand information, but many lawmakers have found it hard to defend Trump in the wake of that testimony.

“The picture coming out of it based on the reporting we’ve seen I would say is not a good one, but I would say also, until we have a process that allows for everybody to see this in full transparency, it’s pretty hard to draw any hard-and-fast conclusions,” Sen. John Thune of South Dakota, the No. 2 Senate Republican, told reporters.

Sen. Roy Blunt, R-Mo., another member of leadership, said, “To some extent, we need to be thoughtful about waiting for the House and whatever conclusions they reach. For us to express concerns about process is totally appropriate. But reaching conclusions based on anybody’s select information at this point probably isn’t a helpful place for us to be.”

For now, Trump’s near-absolute control over his party’s base makes it difficult for Republicans to do anything but cheer him or be uneasy in the shadows, even though polls show that a majority of Americans disapprove of his job performance.

“Everybody in their heart is nervous,” said former Sen. Rick Santorum, a Republican from Pennsylvania. “During the Clinton impeachment, he tried to endear himself to the public as much as possible. But this is the opposite. The base loves him but the president isn’t doing anything to win (other) people over, and that troubles Republicans who have to win support next year from people beyond the base.”