The coming year offers the closest available thing to a do-over. Results in hundreds of local, statewide and federal elections will add up to a ring of dots that, connected, will mark a new set of political boundaries. Whether those new boundaries embrace Trump or wall him out will say a lot about the future of Trumpism in America.

Yet — and here’s the tricky part for Democrats — making 2018 into a year-long referendum on Trump is a recipe for another Election Day shocker. Among other innovations, Trump has demonstrated the limits of the purely negative campaign. Between his own goofs and outrages and the points scored by his enemies in the last election, Trump sank in the polls to depths no normal candidate could survive. Nevertheless, it’s his Diet Coke now filling the White House fridge.

The opposition needs to present a compelling alternative, one that appeals not just to coastal cities and college towns, but to the more centrist and even conservative audiences that vote in the nation’s dwindling swing districts and in the states hostile to Democrats on the 2018 Senate map.