… Pollsters can’t afford to survey each of the 435 House races. Instead they partly rely on a “generic ballot” question, which asks respondents whether they will vote for the unnamed Republican candidate for the House of Representatives in their district, or for the unnamed Democratic candidate.
While individual polls using the generic ballot question can vary greatly, an average of those results usually provides a fairly accurate preview of how the national vote for Congress will break down on Election Day. But the generic ballot question may be less predictive this year, said Joe Lenski, executive vice president at Edison Research, the company that conducts national and state exit polls for the National Election Pool. CONT.
Allison Kopicki, New York Times
Recent polls: U.S. House generic ballot