In Pennsylvania, Sanders’s problem comes in the form of his proposed ban on fracking for natural gas. This is an essential industry in rural Pennsylvania, providing thousands of jobs and economic stimulus to otherwise remote and depressed regions. Democrats in the state are worried that a fracking ban could cost them a state that Trump won by only 44,000 votes in 2016. Evidence from other countries suggests they are right. Australia’s Labor Party lost dramatically in last year’s election in regions near the Adani coal mine in rural Queensland, which climate change activists wanted to close. Sanders could easily do even worse than Clinton did in areas dependent on fracking.

That impact could also drag down local Democratic incumbents. Rep. Matthew Cartwright represents the 8th Congressional District in the state’s northeastern corner. He turned back a challenge in 2018, but Trump carried his district by a whopping 53-44 margin. His seat does not have wells that use fracking, but county governments in his district have received more than $18 million in state revenue derived from fees on fracking. His race is rated a toss-up by the Cook Political Report, and he clearly would prefer to not have to defend Sanders’s fracking ban during the campaign.

These examples are surely just the tip of the iceberg.