The legislative elections in the United States have confirmed the scenario that the polls outlined during the past few weeks, albeit with a margin that few surveys predicted. Democrats regain control of the House of Representatives and the Senate and rack up victories in states where the Republican Party has maintained a dominant position for decades.
The polls were right in identifying the general trend of the electorate, but they fell short when it came to calculating the size of the win. The polls detected the weakening of the Republicans, although the results have exceeded expectations in some of the most hotly contested races, especially in the Senate elections.
Polls anticipated the shift in majorities in Congress
At the start of the campaign, the recovery of the House of Representatives seemed the most achievable target for Democrats. The Senate appeared a harder target due to the territorial distribution of the seats in play and the need to win in states that voted mostly for Donald Trump in 2024.
However, the forecasts changed as autumn progressed. Nate Silver’s FLIPR model, last updated on November 3, considered the Democratic majority in the House of Representatives virtually assured and also pointed to a victory in the Senate.
The evolution of national popular vote polls supported that trend. The averages of voting intention for Congress granted Democrats an advantage close to nine percentage points on the eve of the elections, enough to anticipate a shift in majority in the House of Representatives.
Other models, such as the one developed by Harvard political scientist Gary King, calculated that Democrats would win around 242 seats in the House of Representatives and 53 in the Senate. The result has exceeded those expectations.
Texas and South Carolina smash the forecasts
In Texas, the final average of Nate Silver gave the Democratic candidate James Talarico a 3.3-point advantage over the Republican Ken Paxton in the Senate race. However, with 94% of the expected vote counted, Talarico leads Paxton by 55% to 43%, a considerably larger gap than Democrats could even have imagined.
To this is added Gina Hinojosa’s victory in the governor elections, which has put an end to more than three decades of Republican administrations in Texas. The coincidence of both victories makes the State one of the main settings for Democratic progress.
Also in South Carolina, the Democrat Annie Andrews has defeated the Republican Darline Graham in a Senate election that breaks a long run of Republican victories. Democrats have also managed to seize Senate seats from Republicans in Kansas, Iowa, North Carolina, Ohio and Maine.
The latest polls warned of the possibility that some of these seats could change parties. What they did not anticipate with sufficient precision was the extent of Republican defeats across different electoral categories, from Congress to governorships and state legislatures.
The fear of another poll error has not materialized
As of the close of the polling stations, doubt persisted among U.S. analysts. In several previous elections, especially the presidential elections of 2016 and 2020, the polls underestimated support for Trump and for Republican candidates.
That precedent led to interpreting the Democrats’ advantages from the past few weeks with caution. The possibility that Republican voters would be less willing to respond to polls remained one of the risks for the estimates.
The difference from other electoral cycles is that the Democratic advantage has grown enough to withstand even a multi-point error in favor of the Republicans. The results have confirmed that strength, with victories that in some cases are broader than expected.
The polls get the trend right, but not all of its dimension
The balance is that the final models have correctly identified the shift in majorities in Congress and have detected Democratic progress in states where months earlier it seemed difficult for Republicans to lose, but they fell short when it came to predicting the magnitude of the change in political sign.
In this way, Democrats practically achieve all their objectives by regaining both chambers and exceed their own initial targets in the territorial reach of their victory.