Our most recent book is The Comeback: The 2024 Elections and American Politics. It includes a chapter on congressional and state elections.
Bill Scher at The Washington Monthly:
While it’s likely that Democrats will maintain a healthy generic congressional ballot lead heading into Election Day, the math linking the national House popular vote to House seats is murkier than ever. In 2006, a Democratic 7.9-point popular vote advantage translated to 233 House seats, a net gain of 30. In 2010, the Republicans leveraged a 6.8-point vote edge into 257 seats, a net gain of 63. Eight years later, an 8.4-point margin gave Democrats 40 more seats, bringing their total to 241.
Today, thanks to increased political polarization, geographic sorting, and aerobic gerrymandering, political handicappers envision fewer competitive House districts, which means big popular vote swings may not translate into big numbers of seat flips. That’s why political handicappers such as The Cook Political Report with Amy Walter classify relatively few House districts, just 18, as toss-ups with another 17 as leaning towards one party (12 Democrat, five Republican). The other 400 are considered likely or solidly with a party.
Still, a strong political wind typically blows most toss-up districts towards the popular vote winner. In 2018, Democrats won 21 of the 30 toss-ups, or 70 percent, according to Cook. Moreover, Cook’s race ratings shifted in the Democrats’ favor over the course of the year, as often happens when political analysts receive more district-level poll data. Twelve districts considered toss-ups on May 18 were moved to the “Lean Democratic” or “Likely Democratic” columns by November, and Democrats swept those races. Plus, they picked up three seats from the “Lean Republican” and “Likely Republican” columns.
This November, based on today’s Cook ratings, if Democrats sweep their Lean and Likely races and pick up 70 percent of the toss-ups, they will win 219 seats, just one more seat sufficient for a majority. And that would only mean a net gain of four seats, well below the post-war 25-seat average. A big reason is the explosion of Republican gerrymandering greenlighted by the U.S. Supreme Court’s rollback of the Voting Rights Act, coupled with the Democrats’ loss at the Virginia Supreme Court, scotching their voter-approved gerrymander. As Amy Walter explained to the New York Times, before the judicial rulings, Cook classified 217 House seats as at least leaning Democratic; now that number is down to 207.
