Right now, Republicans have reason for optimism. Historically, turnout among young voters—by far the electorate’s most racially diverse generation—has plummeted in midterm elections compared with the presidential contests that have immediately preceded them. Turnout from presidential to midterm elections has also fallen more modestly among African Americans, and has slipped substantially among Hispanics as well.

Recent polling offers ominous signs for Democrats that this pattern of demobilization could persist in 2018—particularly among young people—despite the Trump administration’s relentless focus on policies that reflect the priorities of his conservative older white base, from ending protection for the Dreamers, to building a border wall, to attempting to repeal the Affordable Care Act. Though surveys show those ideas all face intense resistance among younger adults, Stanley Greenberg, the veteran Democratic pollster, told me there’s a “very real risk” that Millennial turnout could lag again in 2018.

Six months ago, that might not have worried Democrats as much, since polls showed they held an advantage across the age spectrum when voters were asked which party they preferred in the midterm elections. But in recently released surveys from both CNN and the nonpartisan Pew Research Center, voters age 35 and older split almost exactly evenly between the two parties on the generic ballot. Among voters ages 18 to 29, by contrast, Democrats held a resounding 27-point advantage in the Pew survey and an 18-point edge in the CNN poll.