The campaign still has more than a week remaining, and the expectation question is obviously not perfect. When answering, many people may be affected by news media coverage that has also suggested the Republicans are favored to win the Senate — and could be wrong if the traditional polls are misleading. Democrats are hoping that their efforts to turn out voters, including new voters and those who have previously skipped midterm elections, will allow them to win at least a couple of upsets and tossup races.

But the expectation question does have an impressive record.

Over the last 60 years, it has been a better guide to the outcome of presidential races than questions on whom people planned to vote for, according to a 2012 study by Justin Wolfers of the University of Michigan and David Rothschild of Microsoft Research. (Mr. Wolfers has since become a contributor to The New York Times.) The expectation question pointed to the winner in 81 percent of states between 1952 and 2008. The question about voting intentions pointed to the winner in 69 percent.

Asking about expectations, Mr. Rothschild said, allows pollsters effectively to interview “not just the respondents, but a random selection of their social network.”

In 2004, for example, many polls told a confusing story about whether President George W. Bush would win re-election or lose to Senator John Kerry. The expectation question, when asked, consistently pointed to a win by Mr. Bush.