For both parties, the districts most likely to split their tickets are those on the wrong side of the widening class and cultural divide. Based on early counts from both the Daily Kos website and the Democratic Congressional Campaign Committee, Trump carried districts won by 12 Democratic House members. In nine of those 12 districts, the share of whites with a college degree lags below the national average. Seven of the 12 are what we have called “lo-lo” districts, where the total white population and the share of whites with a college degree both trail the national average. Those heavily blue-collar lo-lo districts have become the cornerstone of the GOP congressional majority: Republicans now hold 152 of the 176 districts that meet that description.

The Democrats in the lo-lo districts that Trump carried include Cheri Bustos in Illinois; Dave Loebsack in Iowa; Ron Kind in Wisconsin; Cartwright in Pennsylvania; and three Minnesota incumbents: Tim Walz, Collin Peterson, and Rick Nolan. In all these districts Trump’s margin against Clinton was at least 15 percentage points better than Romney’s against Obama. Though only the Minnesota contingent faced close races in 2016—Kind didn’t even draw an opponent—the strength of Trump’s appeal to working-class whites has moved all of them onto, at the very least, the GOP’s initial target list for 2018 and beyond. “The dam broke this time, and there is more to come,” said Tom Davis, formerly a Republican representative from Virginia and chair of the National Republican Congressional Committee. “You look at northern Minnesota and that dam has broken.”

Bracing for potentially tougher challenges in 2018 and beyond, many of the House Democrats in Trump districts are adopting a common playbook. The two pillars are emphasizing constituent services and focusing as much as possible on bread-and-butter economic issues. “The main point is that the economy outweighs everything else, so these registered Democrats came out and voted for Donald Trump because they’re hurting,” Cartwright said in a recent interview. “Here’s the lesson I take from that: These are my people. They’re hurting. Forget about Donald Trump or Hillary Clinton. My people are hurting. That means I have to redouble my efforts to take care of them. To make sure we do everything we can think of to promote manufacturing jobs in this area, to protect and preserve Social Security and Medicare, and to stimulate the economy so that it works for people around here.”

Likewise, Loebsack, the Iowa Democrat, said in an interview that he considers his accessibility a key to his survival. “For me it’s always been engaging people where they live, work, and play,” he said. “I get around to my counties, every one of my counties, on a very regular basis.”

The other key, Loebsack said, was to stay focused on core economic issues, including local concerns like rural access to broadband or protecting the renewable fuel standard that promotes biofuels. “When people want to talk to me about LGBT issues I talk about them, and I’m for equality,” he said. “When they want to talk about voting rights, I’m for that. But at the same time I think we need to have first and foremost the focus on the economy and jobs.”