The 2018 Democratic Midterm Voters Joe Biden Needs to Retain

But Mr. Biden may not be able to count on the same level of support that Democratic candidates received in 2018. Some of the groups that swung hardest in Democrats’ direction that year have been slow to warm to Mr. Biden. Compared with an authoritative study of the 2018 midterm electorate released this week by the Pew Research Center, recent polls show the party’s presidential nominee lagging behind the rates at which certain key demographics broke for the Democrats two years ago.

To conduct the study, Pew used its American Trends Panel, which tracks a nationally representative sample of Americans and allows researchers to re-contact the same voters over time. Because of its large sample size and because it used a method called voter validation — checking panelists’ responses against publicly available voter files to confirm that they participated when they said they did — Pew’s study is considered more reliable than the national exit polls, which are conducted quickly on the day of the election and undergo minimal adjustments afterward.

Midterm elections after a new president has taken office always tend to be tough for the president’s party. Yet midterm voters also tend to skew slightly more affluent and conservative than general-election voters. So the surge in Democratic votes across the board, particularly among key groups, appears to tee up Mr. Biden for a strong showing.

Latinos, white suburbanites and young voters swung especially hard in Democrats’ favor in 2018, as the Pew study reflected, sometimes even more starkly than the exit polls. Here’s a look at what the Pew study tells us about those groups, and at where things stand now.

Young voters

Youth enthusiasm and participation ran low in the 2016 general election, but voters under 30 grew heavily involved in 2018 — doubling their participation rate from the previous midterms, according to an analysis by the United States Elections Project at the University of Florida. No other age group jumped by as much.