As flooding forced many from their homes, most residents pointed to more tangible culprits than the climate: the failure to dredge the Lumber River; a gap in the city’s levees.

“The climate and stuff, that’s God’s work,” said Rodney Locklear, a 62-year-old forklift driver, whose home was one of the few on Canal Street not made uninhabitable by the rising waters. “If man was in control of the climate, he’d have a grudge against someone and hell, he wouldn’t give him no sun — wouldn’t give him no rain, no wind.”

In polls of voters’ top priorities, climate change rarely garners more than 7 to 10 percent, trailing health care, jobs and immigration. For a passionate core, it resonates. But to the enduring frustration of environmental activists, that core has proved limited. Among Democrats, 45 percent said health care was the issue they most wanted the party to tackle if it regains power in Washington, according to a survey this year by Civis Analytics. Climate change was far below, at 7 percent.

“Until voters in the U.S. perceive this as a quite imminent threat, it’s liable to remain mired in the middle of all the other issues,” said Jeff Nesbit, the executive director of Climate Nexus, a group seeking new ways to communicate the threat of climate change, and the author of a recent book, “This Is the Way the World Ends.”

According to an in-house database compiled by Climate Nexus on 161 potentially competitive House races, only a small handful of candidates have released TV ads or online videos prominently featuring climate and energy issues.

Even the Democratic megadonor Tom Steyer, who poured tens of millions of dollars since 2010 into raising awareness of climate change, has shifted focus this year. Mr. Steyer is spending over $30 million to help Democrats take back the House by focusing on voters under 35, whose failure to turn out in off-year elections was a reason Democrats suffered losses in previous midterms.