There is, however, one intriguing weak spot for Democrats among the youngest millennials: minorities. While young whites are far more Democratic than their elders, the youngest nonwhite adults tend to be somewhat more Republican than their elders.

According to the Pew data, 17 percent of 18- to 25-year-old black adults lean Republican — far more than any other age group among blacks. The sample is small — there were just 354 black adults between the ages of 18 and 25 queried — but it is not the only piece of evidence supporting this possibility. In the 2012 exit polls, just 80 percent of black men 18 to 29 supported Mr. Obama, although the number of respondents was quite low.

The Pew data also shows Republicans faring somewhat better among the youngest Hispanics. Thirty-two percent of the youngest Hispanics lean Republican, but Republicans didn’t exceed 26 percent with any other age bracket among Hispanics.