While the polling industry has taken a lot of guff in recent years, one question continues to earn its keep: the generic congressional ballot test. It is a poll question that asks respondents which party’s candidate they plan to support to represent their House district. The average lead in the general congressional ballot test can’t tell us exactly how many seats will flip, but it can tell us if a wave is coming.
Three of the last five midterm elections have been “wave” years in which the party that did not control the White House flipped over 25 House seats—the post-World War II average—en route to seizing the Speaker’s gavel. In each of the wave years—the 2006 and 2018 Blue Waves, as well as the 2010 Red Wave—the Real Clear Politics average generic congressional ballot test lead for the opposition party cleared five points. At no point in the non-wave years of 2014 and 2022 did either party meet that mark (though Republicans came close in 2022, briefly touching 4.8 in April).
This year, Democrats have already cleared the five-point mark in the RCP average, first for a few days in February, then again in late March. This spring, the Democratic lead has steadily ticked upward. Buoyed by particularly strong data in the latest New York Times poll, the Democrats’ lead stood at 7.2 points as of May 18. That nearly matches the 7.3-point poll lead Democrats had before Election Day 2018.
That’s significant for two reasons. One, no party has built an average seven-point generic congressional ballot test lead in RCP this early in a midterm year since 2006, when public ire over the Iraq War quagmire, the botched response to Hurricane Katrina, and the unpopular and unsuccessful push to privatize Social Security partially fueled double-digit Democratic polling leads from the very beginning of the year.
Two, in the RCP average, no party that led by seven points at some point during a midterm year ever ended the election year with a lead of less than seven points. In the more crucial metric of the aggregate House popular vote margin, that’s also pretty much true, although the 2010 Republicans scored slightly below at 6.8 points.
Of course, there can always be a first time. Perhaps President Donald Trump gets the Strait of Hormuz reopened, which eases pressure on gas prices and prompts a voter reassessment. But most energy industry experts have cautioned that even with a resolution with Iran, prices may not return to pre-war levels, partly because of damage to energy infrastructure. More likely, we are seeing a dynamic familiar in wave years—year-long, stable polling leads for the opposition party. (An exception was in 2010, when Democrats were competitive in generic ballot polls through June before Republicans broke away.)
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.
If Democrats maintain a national poll edge of seven points or more by November, some races considered toss-ups would likely shift into the Democratic column, some once-GOP-leaning districts would become toss-ups, and the final Democratic net seat gain could reach double-digits. But aggressive gerrymandering and calcifying polarization are limiting the size of midterm waves and lowering the potential ceiling on seat flips.
Strong indications of a Blue Wave may prompt the Trump administration to adopt extreme measures to prevent big losses. I’m don’t usually dwell on the darkest of scenarios, but the insane lengths to which Trump went to try to steal the 2020 election make it impossible to rule anything out. Democrats may need not only a strong electoral performance but also a strong legal performance to protect the vote in the run-up to the election and the days after.
The bottom line: Democrats are in historically strong shape for the midterms, with all forecasts pointing to a Blue Wave. And they may need every drop of it.
