A growing number of Republicans are privately warning of increasing fears of a total wipeout in 2020: House, Senate, and White House.

Why it matters: All of this is unfolding while the economy still looks strong, and before public impeachment proceedings have officially begun.

House Republicans in swing districts are retiring at a very fast pace, especially in the suburbs of Texas and elsewhere. (Republicans talk grimly of the "Texodus.") Rep. Greg Walden — the top Republican on the House Energy and Commerce Committee, and the only Republican in Oregon's congressional delegation — yesterday shocked the party by becoming the 19th GOP House member to not seek re-election.

The Republican Senate majority, once considered relatively safe, suddenly looks in serious jeopardy. Democrats are raising more money, and polling better, than Republican incumbents in battleground after battleground.

President Trump trails every major Democratic candidate nationally and in swing states — and his favorable ratings remain well under 50%.

The biggest recent change is Republicans' increasingly precarious hold on the Senate.

National Journal's Josh Kraushaar writes in his "Against the Grain" column that "the pathway for a narrow Democratic takeover of the upper chamber is looking clearer than ever": "If Trump doesn’t win a second term, Democrats only need to net three seats to win back the majority."

Scott Reed, the U.S. Chamber of Commerce senior political strategist, tells me that third-quarter fundraising reports showing three Republican senators being out-raised by Democratic challengers (in Arizona, Iowa and Maine) "are a three-alarm fire."

"The party was shaken by that," Reed said. "We're all worried."

The well-funded Chamber started TV ads in Arizona last week, launches an ad today in Maine, and will add a third state next week.

That's the earliest the group has ever gone on the air: Ads typically begin after Thanksgiving or New Year's.

"We have to spend early because the climate stinks," Reed said. "All these incumbent senators have terrible job approvals and terrible favorables."

But Reed thinks Trump has a better than 50-50 chance of hanging on: "He's still wildly popular in the middle of the country."

Between the lines: Across the board, struggling Republican Senate campaigns are more concerned about lousy fundraising than they are with poor polling.

Republican strategists and campaign staffers said that with the polarization of the Trump era, key House and Senate races will depend even more than usual on the presidential race.

What to watch: Senate races look so tight that control could be decided by a January 2021 runoff in Georgia.

Go deeper: Trump's Senate red wall