WASHINGTON — As Republican leaders scramble to stave off a Democratic wave or at least mitigate their party’s losses in November, a strategy is emerging on the right for how to energize conservatives and drive a wedge between the anti-Trump left and moderate voters: warn that Democrats will immediately move to impeach President Trump if they capture the House.

What began last year as blaring political hyperbole on the right — the stuff of bold-lettered direct mail fund-raising pitches from little-known groups warning of a looming American “coup” — is now steadily drifting into the main currents of the 2018 message for Republicans.

The appeals have become a surefire way for candidates to raise small contributions from grass-roots conservatives who are devoted to Mr. Trump, veteran Republican fund-raisers say. But party strategists also believe that floating the possibility of impeachment can also act as a sort of scared-straight motivational tool for turnout. Last week, Senator Ted Cruz of Texas used his re-election kickoff rally to introduce a video featuring a faux news anchor reading would-be headlines were conservatives not to vote in November.

“Senate Majority Leader Schumer announced the impeachment trial of President Trump,” one of the anchors says.