Their biggest losses are among young white men who went from favoring Democrats over Republicans 48-36 in 2016 to favoring Republicans over Democrats 46-37 in 2018.

From Reuters:

The online survey of more than 16,000 registered voters ages 18 to 34 shows their support for Democrats over Republicans for Congress slipped by about 9 percentage points over the past two years, to 46 percent overall. And they increasingly say the Republican Party is a better steward of the economy.