President Trump Donald John TrumpFederal prosecutor speaks out, says Barr 'has brought shame' on Justice Dept. Former Pence aide: White House staffers discussed Trump refusing to leave office Progressive group buys domain name of Trump's No. 1 Supreme Court pick MORE is in new and dangerous territory this week, as some Republicans and administration veterans express unease about his actions, and polls show rising support for impeachment.

Voices that are normally supportive of the president have fallen silent, partly out of fear that new revelations could be around the corner.

ADVERTISEMENT

A CBS News-YouGov poll released Sunday showed majority support for an impeachment inquiry, with 55 percent of respondents nationwide in favor and 45 percent opposed.

A CNN-SSRS poll released Monday showed plurality support for the most dramatic move of all — Trump’s impeachment and removal from office. The CNN poll indicated 47 percent support for such a move among all adults surveyed, with 45 percent against.

Peter Wehner, who served in the administrations of the past three Republican presidents before Trump, said that Trump asking Ukrainian leader Volodymyr Zelensky to help dig for dirt on 2020 Democratic front-runner Joe Biden Joe BidenFormer Pence aide: White House staffers discussed Trump refusing to leave office Progressive group buys domain name of Trump's No. 1 Supreme Court pick Bloomberg rolls out M ad buy to boost Biden in Florida MORE was potentially more serious than other controversies.

“What happened has penetrated beyond anything else Trump has done. Republicans are afraid of that,” said Wehner, a persistent critic of the president.

Referring to GOP support for Trump up to this point, Wehner added, “The only thing that will change that dynamic is if members decide that standing with Trump is a mortal threat to their political lives. But that could happen.”

The GOP is clearly not at the breaking point yet. But figures beyond the ranks of the usual Trump critics have expressed dissent in recent days.

Tom Bossert, Trump’s former homeland security adviser, gave interviews to both ABC News’s “This Week” and The New York Times on Sunday in which he said he was “deeply disturbed” by the president’s behavior with Zelensky. Bossert also said he was “frustrated” with Trump’s personal lawyer Rudy Giuliani Rudy GiulianiThe Hill's Campaign Report: GOP set to ask SCOTUS to limit mail-in voting CIA found Putin 'probably directing' campaign against Biden: report Democrats fear Russia interference could spoil bid to retake Senate MORE and others for repeating to Trump a “debunked” conspiracy theory involving Ukraine.

On “This Week,” Giuliani shot back, “Tom Bossert doesn’t know what he’s talking about.”

But Bossert isn’t the only dissonant voice Team Trump has to worry about.

On Sunday, Rep. Adam Kinzinger Adam Daniel KinzingerFox News reporter defends confirming Atlantic piece despite Trump backlash: 'I feel very confident' GOP lawmaker defends Fox reporter after Trump calls for her firing Lindsey Graham: 'QAnon is bats--- crazy' MORE (R-Ill.) called a Trump tweet “beyond repugnant.” Trump had amplified a comment from a conservative pastor who told Fox News that removing the president could lead to “civil war.”

Trump has also received criticism from Sen. Mitt Romney Willard (Mitt) Mitt RomneyCrenshaw looms large as Democrats look to flip Texas House seat The Hill's Morning Report - Sponsored by Facebook - Republicans lawmakers rebuke Trump on election Trump dumbfounds GOP with latest unforced error MORE (R-Utah) and a handful of other more predictable critics.

The president and his allies must also contend with potential discomfort from other figures stepping into the spotlight.

Secretary of State Mike Pompeo Michael (Mike) Richard PompeoWatchdog confirms State Dept. canceled award for journalist who criticized Trump Trump's push for win with Sudan amps up pressure on Congress Putin nominated for Nobel Peace Prize MORE on Tuesday sought to block congressional testimony from Marie Yovanovitch, the former U.S. ambassador to Ukraine, and Kurt Volker, who resigned his position as special envoy to Ukraine on Friday.

On Tuesday afternoon, it was confirmed that Volker and Yovanovitch would nevertheless give depositions.

Trump spoke negatively about Yovanovitch in his phone call with the Ukrainian president, while Volker may know more than has yet been revealed about Giuliani’s activities in the country.

Other voices within the national security establishment now estranged from Trump, including former national security adviser John Bolton John BoltonJudge appears skeptical of Bolton's defense of publishing book without White House approval Maximum pressure is keeping US troops in Iraq and Syria Woodward book trails Bolton, Mary Trump in first-week sales MORE and former Director of National Intelligence Dan Coats Daniel (Dan) Ray CoatsFBI chief says Russia is trying to interfere in election to undermine Biden The Hill's Morning Report - Sponsored by The Air Line Pilots Association - Trump, Biden renew push for Latino support Former Intel chief had 'deep suspicions' that Putin 'had something on Trump': book MORE, also have the capacity to make trouble should they wish to do so.

The White House even suffered a jab from the intelligence community inspector general on Monday. The inspector general’s office issued a news release that pushed back on suggestions from Trump and Sen. Lindsey Graham Lindsey Olin GrahamLincoln Project mocks Lindsey Graham's fundraising lag with Sarah McLachlan-themed video The Hill's Morning Report - Sponsored by Facebook - Republicans lawmakers rebuke Trump on election Trump dumbfounds GOP with latest unforced error MORE (R-S.C.) that the rules governing complaints had been changed to facilitate the whistleblower whose concerns sparked the current controversy.

More broadly, Republicans look ahead and fear the unknown.

GOP strategist John Feehery noted that while some elected officials were supporting Trump, others were keeping quiet for now.

“Some people are just kind of waiting to see what the next revelations are,” said Feehery, who is also a columnist for The Hill. “Most Republicans don’t really love this president but they respect his power with the Republican base.”

Feehery, who said that he saw no reason to impeach the president, also warned Democrats that they could engender a backlash if they were seen by voters as colluding with the media to make “lots of mountains out of molehills.”

Trump allies also say the president could have some success in pushing back against the impeachment efforts if the process becomes prolonged. Former special counsel Robert Mueller Robert (Bob) MuellerCNN's Toobin warns McCabe is in 'perilous condition' with emboldened Trump CNN anchor rips Trump over Stone while evoking Clinton-Lynch tarmac meeting The Hill's 12:30 Report: New Hampshire fallout MORE did see some signs of erosions of public confidence during his tenure, after he was attacked for months on end by Trump’s supporters.

Still, the nature of the current controversy makes it especially incendiary. The story is simple, unlike the Russia-related allegations investigated by Mueller. The whistleblower’s account has been borne out by the White House’s own memorandum of the Trump-Zelensky phone call. And the whole matter pertains to national security, where Republicans like to boast of their strength.

“The president must realize that the same partisanship that has kept him unaffected [by previous controversies] could turn against him in a second,” said Princeton history and public affairs professor Julian Zelizer. “It’s about party power. For Republicans, if it is no longer in their interest to support the president, they will cut ties with him.”

Zelizer did not suggest that such a moment was imminent. But he also highlighted the danger for Trump in new facts emerging — and cited an ominous historical parallel.

“The Watergate investigation was discovering facts that continued to shock, and continued to break political support” for former President Nixon, he said. “That is why it is even a question now, as to whether Trump can hold on to Republican voters.”

The Memo is a reported column by Niall Stanage, primarily focused on Donald Trump’s presidency.