To the old-fashioned, it might seem crazy that the Republicans plan to fight the 2018 election as a referendum on a Trump impeachment.

Traditional wisdom was: If the president of your party is unpopular, try your utmost to de-nationalize off-year elections. Focus the voters on local issues and down-ballot candidates! “Maybe you don’t like Trump. But you like the new factory openings in our district, don’t you?”

So why are Republicans edging toward the opposite approach?

The short answer: They have no choice. The old saying, “All politics is local,” is outdated. All politics is national. In his forthcoming book, The Great Alignment, the political scientist Alan Abramowitz argues that national-party ID holds an overwhelming sway over local results. This election will be about the president, as 2014 and 2010 and 2006 were about the president. Republicans might as well face up to that fact. Rather than run away from an association that cannot be escaped, it’s tactically smarter to embrace the association and try to mobilize such turnout as can be mobilized in at-risk seats like the one they lost in the Pennsylvania special election of March 13, 2018.

The impeachment issue works because it speaks to reluctant Trump supporters, the “I wish he wouldn’t tweet so much” brigade. Message to them: If you stay home, you’re not just teaching the president a lesson, enabling a course correction on the way to the next presidential election. You’re actually voting in that presidential election now, whether you know it or not. So show up and vote for two more years!