Republicans fear potential impeachment move if Democrats win in 2018

"POTUS is aware" of the concern, one White House source said, describing the hand-wringing inside the West Wing over the upcoming midterms as "the anticipation of death."

Hoping to avert that potential scenario Trump is expected to campaign hard for House Republicans in the November elections, the source said, citing internal White House planning.

"(Trump) doesn't want anyone to say he didn't fight hard to keep the House," the source added.

However, not all Democrats believe that impeachment is the path to victory for 2018.

"Let the investigation play out. In the meantime, our focus should be on demonstrating why we will do more for families than the GOP and expose the reckless waste and abuse of government resources in this administration," former Hillary Clinton campaign manager Robby Mook told CNN. "We do that by subpoenaing records and getting them out in the open so taxpayers can see how badly they're being ripped off."

GOP fears

In the House, the prevailing concern among Republican lawmakers is that House Minority Leader Nancy Pelosi will have no choice but to initiate impeachment proceedings should she succeed in seizing the speaker's gavel.

"I'm sure Pelosi will have immense pressure from the base to impeach," a top GOP congressional aide added.

"That's logical," another senior Republican aide in the House said.

The fears of a wave election that would sweep Republicans from power in the House and perhaps usher in Democrat-led impeachment proceedings in 2019 are now heightened with the coming exit of Speaker Paul Ryan.

One White House official said there are worries among the President's aides that Ryan's choice not to seek re-election might signal to other members who are concerned about losing their races that they shouldn't run, either.

A source familiar with Ryan's thinking said the speaker understands that much of Washington will read his announced departure as a something of a concession that Democrats are likely to take the House.

"He is well aware what some may say but also quite sure no battleground district or race will be decided based on his decision," the source said. "No one has put Republicans in a better place to hold the majority than the speaker."

Mook is not as optimistic that Democrats will sweep the House: "Democrats need to remember that gerrymandering is real and we have to win well over a majority of the national vote to win the House. This is harder than it looks."

Democrats' outlook

Progressive political strategist Julian Mulvey -- a veteran of the 2016 Bernie Sanders presidential campaign -- is working on a number of 2018 races across the country, from Ben Jealous in Maryland to Nancy Soderberg in Florida.

"What (Sanders) continues to say is we shouldn't jump the gun on impeachment. I think that's absolutely right," he said. "There's going to be increasing pressure to do so, but at this moment in time, that's not the Democratic message and that shouldn't be the core of the Dem message. He's right to hold people off of that."

Mulvey adds that Democrats should be approaching the issue of invoking impeachment on a "case-by-case" basis.

"In a competitive primary, you do what's right," he told CNN, adding that Democratic candidates should be messaging around "health care and tax cuts for the rich," not impeachment.

Despite that caution from progressive strategists, one House Democratic lawmaker who asked not to be named said a decision by Trump to fire special counsel Robert Mueller would lead the party to be much more aggressive.

"If he fires Mueller you'll see every Democrat call for impeachment," the congressman said.

White House press secretary Sarah Sanders told reporters Wednesday that Trump is counting on GOP lawmakers to not make any plans to leave Congress.

"We certainly hope that Republicans will continue to remain in the House, particularly those that support the President's agenda," Sanders said.

Dan Pfeiffer, former senior adviser to President Barack Obama, believes the GOP's worries are purely a tactical effort to rev up the base.

"I think it is a desperate attempt to juice a depressed Republican base," he said.