Posing for the cameras with a photogenic dog is something of an election campaign cliche, but as Ed Davey picks up Marvin, an affectionately squirming norfolk terrier, the intended message is about something much less obviously appealing: sewage. The Liberal Democrat leader is posing with a series of dogs and their owners on Eastbourne beach, a local election stop intended to bring attention to an issue his party has campaigned on enthusiastically for the past two years, and with increasing cut-through. As Davey leads Marvin along the shingle, 60 miles away in west London the environment secretary, Thérèse Coffey, is announcing a series of partly recycled policies to clean up waterways, an explicit acknowledgment of the damage the issue is causing to the government. Lib Dem research shows pollution outflows, both on beaches and into rivers and chalk streams, is one of the most pertinent issues for voters in affected areas ahead of the local elections on 4 May. Josh Babarinde, a Lib Dem councillor in Eastbourne who is also the candidate for the Conservative-held parliamentary seat, a key target for the party, says sewage is raised spontaneously as often as the NHS during local door knocking. “It is one of the most common issues that comes up on the doorstep. Beaches are the lifeblood of this town.” Speaking after the next leg in his day of campaigning, a tour around the vast and hi-tech warehouse of a locally based book wholesaler, Davey says sewage has even supplanted that perennial issue in local elections, the pothole. “It’s much bigger than potholes,” he said. “Potholes are a very serious issue, and they do move votes, but for sewage, the reason why it’s so dramatic is it brings the pollution of our natural environment and the damage that it’s doing to our rivers and our seas, and wildlife and plants and animals, to human health.” The rise of sewage as an electoral issue is notable for several reasons, one of which is how the Lib Dems chipped away at it for so long without notable interest from other parties. It reached Lib Dem campaigners’ radar when voters in Chesham and Amersham kept bringing it up before the party’s stunning byelection victory over the Conservatives in June 2021, the starting point for the idea of a “blue wall” of vulnerable Tory commuter belt seats. “When we started talking about sewage two years ago, the other parties though it was a bit weird,” says one Lib Dem official. “But now they all want to talk about it.” This is very much the case. Last week, before Coffey’s plan for cleaner water emerged, a group of Conservative MPs representing Sussex seats met jointly with Southern Water and the Environment Agency in an attempt to spur action on a subject many fear is electorally damaging to them. Labour, too, is very much aware of the subject, with Keir Starmer accusing the government last week of “turning Britain’s waterways into an open sewer”. But sewage has particular electoral resonance for the Lib Dems as it ties into a wider narrative the party has perceived and exploited in Conservative-held areas: former Tory voters becoming disenchanted with a government they feel is out of touch and takes them for granted. “It’s the classic environmental issue where you’re despoiling a public good, and it’s the government’s responsibility to stop it through regulation,” says Davey, whose local election campaign schedule involves, as one official put it, “a sewage-related visit more or less every day”. This set of local elections is, Davey says, in effect a dry run for a general election expected next year, not least as internal party polling suggests a majority of former Tory voters who switch to the Lib Dems in May will stay with them. This set of seats was last fought in 2019, when the Lib Dems won more than 700 councillors as the Conservatives and Labour struggled under the leadership of Theresa May and Jeremy Corbyn respectively. Defending those seats, let alone winning more, is a tough ask, but Davey is confident the party, riding what could be termed a sewage tidal wave, can do it. “Doing better than 2019, perhaps our best local elections ever, would really be something,” he said. “I think it would send a real shiver amongst the Tories. They would see us coming for them.”