A torrent of impeachment developments has triggered a reckoning in the Republican Party, paralyzing many of its officeholders as they weigh their political futures, legacies and, ultimately, their allegiance to a president who has held them captive.

President Trump’s efforts to pressure a foreign power to target a domestic political rival have driven his party into a bunker, with lawmakers bracing for an extended battle led by a general whose orders are often confusing and contradictory.

Should the House impeach Trump, his trial would be in the Senate, where the Republican majority would decide his fate. While GOP senators have engaged in hushed conversations about constitutional and moral considerations, their calculations at this point are almost entirely political.

Even as polling shows an uptick in support nationally for Trump’s impeachment, his command over the Republican base is uncontested, representing a stark warning to any official who dares to cross him.

Across the country, most GOP lawmakers have responded to questions about Trump’s conduct with varying degrees of silence, shrugged shoulders or pained defenses. For now, their collective strategy is simply to survive and not make any sudden moves.

This account of the anxiety gripping the Republican Party is based on interviews with 21 lawmakers, aides and advisers, many of whom spoke on the condition of anonymity to talk candidly.

Trump has been defiant in his defense, insisting his conduct with foreign leaders has been “perfect” and claiming a broad conspiracy by the Democratic Party, the intelligence community and the national media to remove him from office. Yet few Republican lawmakers have been willing to fully parrot White House talking points because they believe they lack credibility or fret they could be contradicted by new discoveries.

“Everyone is getting a little shaky at this point,” said Brendan Buck, who was counselor to former House speaker Paul D. Ryan (R-Wis.). “Members have gotten out on a limb with this president many times only to have it be cut off by the president. They know he’s erratic, and this is a completely unsteady and developing situation.”

Republican officials feel acute pressure beyond Trump. The president’s allies on talk radio, Fox News Channel and elsewhere in conservative media have been abuzz with conspiratorial talk of a “deep state” coup attempt and accusations that House Intelligence Committee Chairman Adam B. Schiff (D-Calif.) and House Democrats are corrupting the impeachment process.

The GOP’s paralysis was on display this past week in Templeton, Iowa, where a voter confronted Sen. Joni Ernst (R) at a town hall meeting Thursday over her silence about Trump’s conduct.

At an event in Templeton, Sen. Joni Ernst (R-Iowa) was confronted by a constituent over her response to the whistleblower complaint that sparked impeachment. (Joyce Koh/The Washington Post)

“Where is the line?” Iowa resident Amy Haskins asked in frustration. “When are you guys going to say, ‘Enough,’ and stand up and say, ‘You know what? I’m not backing any of this.’ ”

“I can say, ‘Yea, nay, whatever,’ ” Ernst replied. “The president is going to say what the president is going to do.”

Trump’s extraordinary public request that China investigate 2020 Democratic presidential candidate Joe Biden — adding to his previous pressure campaign on Ukraine — has sparked divergent reactions among other Republican senators, including over whether the president was being serious when he delivered his plea.

Sen. Mitt Romney (R-Utah), the most outspoken of his colleagues, tweeted Friday: “By all appearances, the President’s brazen and unprecedented appeal to China and to Ukraine to investigate Joe Biden is wrong and appalling.”

By contrast, Sen. Marco Rubio (R-Fla.) dismissed it as a joke. “I don’t know if that’s a real request or him just needling the press, knowing that you guys were going to get outraged by it,” Rubio told reporters.

On Saturday, Trump on Twitter swatted back at Romney by calling him “a pompous ‘ass’ who has been fighting me from the beginning” — a flashing signal to other Republicans that there would be consequences to speaking out against the president.

Colin Powell, who served as secretary of state under George W. Bush, said during a panel sponsored by the New Albany Community Foundation in Ohio that “the Republican Party has got to get a grip on itself. Republican leaders and members of the Congress . . . are holding back because they’re terrified of what will happen [to] any one of them if they speak out.”

Some House Republicans have tried to offer a more forceful defense than their Senate compatriots.

But House Minority Leader Kevin McCarthy’s shaky appearance last weekend on CBS’s “60 Minutes” was widely panned, even among senior GOP aides, and raised questions about whether he was up to the task of protecting Trump. The California Republican falsely accused his interviewer, Scott Pelley, of misrepresenting a key phrase in the transcript of Trump’s July 25 call with the Ukrainian president.

But some Trump aides privately said the president likes the messages sent by surrogates such as McCarthy and White House policy adviser Stephen Miller, who are willing to sit for a grilling and disparage the media, according to two Republicans close to the president.

Rep. Mark Meadows (R-N.C.), an informal Trump adviser, insisted the president had done “nothing wrong” and denounced those who act “as if he’s guilty until he’s proven innocent.”

“For Republicans to get weak, well, they have a very short memory,” Meadows said, noting that his colleagues facing competitive primary races will need Trump’s support.

Former Republican senator Jeff Flake, a Trump antagonist, said his former colleagues believe the foreign leader interactions under investigation in the House represent “new territory” compared with past challenges, including the Russia investigation.

“There is a concern that he’ll get through it and he’ll exact revenge on those who didn’t stand with him,” Flake said. “There is no love for the president among Senate Republicans, and they aspire to do more than answer questions about his every tweet and issue. But they know this is the president’s party and the bargain’s been made.”

The responses from most Republicans have infuriated and distressed Democrats, who consider Trump’s conduct a brazen and unconstitutional abuse of power.

“My Republican colleagues’ silence seems unsustainable and inexcusable, given the threat to our national security as well as the integrity of our democratic institutions,” said Sen. Richard Blumenthal (D-Conn.).

The frenetic reactions underscore how Republicans are navigating this moment on their own, without direction from the White House or clear guidance from the congressional leadership.

Many Republicans also said in interviews last week that Trump’s ability to nominate and confirm dozens of conservative federal judicial nominees and pass an overhaul of the tax code makes it harder to argue to their voters that he is now a burden on the party’s policy agenda.

This is not the first such crossroads, of course. Republicans largely stood behind Trump in 2016 after the release of the “Access Hollywood” tape on which he bragged of sexual assault, as well as during the darkest days of the Russia investigation and in the wake of racist comments.

“It feels like we’ve been constantly moving the line,” said Tom Rath, a GOP fixture in New Hampshire. “We say, ‘Don’t cross this line.’ Okay, you crossed it. So, ‘Don’t cross this line.’ We’re finally at a point where patience is exhausted, reason is exhausted and, quite frankly, the voters are exhausted.”

A Republican strategist who is close with several senators and spoke on the condition of anonymity to share a candid assessment called the situation “a disaster.” This consultant has been advising clients to “say as little as possible” about impeachment developments to buy time.

Since last month’s whistleblower complaint sparked the impeachment inquiry, 48 percent of Americans support impeachment and 46 percent oppose it, according to an average of polls analyzed by The Washington Post. Among Republicans, however, 11 percent support impeachment and 86 percent oppose it, the analysis found.

“There just hasn’t been pushback, and in part it’s because of this perception that he’s like Rasputin with the base with magic powers,” said GOP consultant Mike Murphy, a Trump critic.

Fox News personality Tucker Carlson, who is admired by Trump and occasionally speaks with him, co-wrote an essay in the Daily Caller last week offering a road map for Republicans, writing that “there’s no way to spin” Trump’s request that a foreign leader investigate one of his domestic opponents as proper, but that it did not rise to the level of an impeachable offense.

Veteran party figures said a true break with Trump is possible, but could take months, if not years. Senate Republicans are taking their cues from Majority Leader Mitch McConnell (R-Ky.), a taciturn operator who has labored to maintain an uneasy but transactional relationship with Trump.

Though a loyal Republican, McConnell has a history of expressing public concern with an embattled president in his own party. In 1973, McConnell, then a budding Kentucky politician, called the Watergate affair “totally repugnant” and denounced the conduct of President Richard Nixon and some in his administration, as documented by McConnell biographer John David Dyche.

In a new campaign ad released over the weekend, McConnell remained firmly at Trump’s side, saying, “The way that impeachment stops is a Senate majority with me as majority leader.”

Other than Romney and Sen. Ben Sasse (R-Neb.), who also has criticized Trump’s conduct with Ukrainian and Chinese counterparts, others who might break with the president include Lamar Alexander of Tennessee, who is retiring next year, and Senate Intelligence Committee Chairman Richard Burr of North Carolina, according to two top Republicans in close touch with senators.

Still, many more Republicans would have to join them to reach the two-thirds majority in the upper chamber required to convict the president and remove him from office.

“Nobody wants to be the zebra that strays from the pack and gets gobbled up by the lion,” a former senior administration official said in assessing the current consensus among Senate Republicans. “They have to hold hands and jump simultaneously … Then Trump is immediately no longer president and the power he can exert over them and the punishment he can inflict is, in the snap of a finger, almost completely erased.”

Yet with Washington as polarized as at any time in recent history, political winds may not blow strongly enough. As long as impeachment is a Democratic priority driven by House Speaker Nancy Pelosi (Calif.), it will be difficult — if not impossible — for Senate Republicans to get on board, argued Alex Castellanos, a longtime GOP strategist.

“The more passions swell in Pelosi’s world, the more McConnell will deflate them,” Castellanos said. Impeachment proceedings, he predicted, will be “an overhyped movie with an unsatisfying end.”

Rachael Bade and Emily Guskin contributed to this report.