Democratic 'Blue Wave' Approaches: Will Trump Reenact the 2018 Midterm Election Script?

According to PolyBeats monitoring, as of September 24, the probability of a "blue wave" in the midterm elections on the prediction market Polymarket rose from 65% in June to 86%. According to the market definition, a "blue wave" requires Democrats to simultaneously secure 218 House seats and 49 Senate seats after the midterm elections.

2018 was the most recent U.S. midterm election widely described as a "blue wave." Democrats gained a net of about 41 House seats, ultimately reclaiming the House with 235 seats to 199; however, the Senate did not flip blue in tandem, and Republicans instead expanded their advantage. Post-election surveys showed that 64% of voters said Trump influenced their congressional vote. Healthcare and immigration were also key Democratic issues, and pre-election surveys showed Democratic candidates were more trusted by voters on these two issues.

Recent polls have provided Democrats with tailwinds. A Marist poll released on September 23 showed that among registered voters, Democrats led Republicans by 12 percentage points, 53% to 41%, in the generic congressional ballot; among independents, the Democratic lead was even larger. The survey also showed Trump's approval rating at 39% and disapproval at 59%, with many voters saying their personal financial situation had worsened compared with a year earlier.