Some Republicans are sounding the alarm over Donald Trump’s devastating effect on their support among suburban voters.

The latest evidence of panic came in a secret audio recording of a conversation between Dennis Bonnen, speaker of the Texas house of representatives, and an influential conservative activist.

According to the Washington Post, Bonnen can be heard saying: “I just think we’ve got to get through 2020, guarantee if we try and hold this majority – which, with all due respect to Trump, who I love by the way – he’s killing us in the urban-suburban districts.”

The hour-long recording was made public on Tuesday by Michael Quinn Sullivan, chief executive of far-right pressure group Empower Texans, hours before a court hearing where a judge would be asked to order its release.

In the conversation, Bonnen can reportedly be heard asking Sullivan to target certain Republicans ahead of the party’s primary elections next year, while also using profane language to describe Democrats.

A “suburban revolt” against Trump’s vulgarity and inertia on issues such as gun violence could make or break his presidency and wider Republican hopes in November 2020. Democrats swept to victory in last year’s midterm elections partly based on suburban voters, taking back the House of Representatives, where an impeachment inquiry against Trump is now under way.

Democratic wins in the suburbs included a district in South Carolina they had not won for 40 years, the one-time Ronald Reagan stronghold of Orange county, California, and parts of Texas itself. Although Democrat Beto O’Rourke fell short against Republican Ted Cruz in a Texas Senate race, his surge fuelled hopes that Democrats can even turn the Lone Star state blue.

In the aftermath of the midterms, Eric Cantor, the former Republican House majority leader, wrote in the New York Times: “There is no doubt that some of the loss in support this year from college-educated women, for example, is a result of the negative opinion these voters have of President Trump.

“But it is also true that Republicans have not had much to offer suburban voters on what they consistently say are their top issues, including health care, child care, education, the environment and transportation.”