Fundamental conditions drive election outcomes. But in this odd campaign, the fundamentals conflict. Once-familiar political signals are muffled. That makes predictions hazy — still. Consider the economy. The unemployment rate has declined to 5.9 percent from 7.9 percent in January 2013. The Dow Jones industrial average has risen more than 25 percent in the same period. In the third quarter of this year, the overall economy grew at a healthy 3.5 percent rate, completing the strongest six-month period of growth in more than a decade.

In part, the failure of those gains to brighten the public mood reflects the nature of the modern economy. Benefits flow disproportionately to a high-earning minority, while average families struggle. Mr. Obama and fellow Democrats themselves invoke those struggles as the reason to enact their economic proposals. It also reflects the long-term trend toward partisan polarization. Rising numbers of voters interpret economic developments through the prism of political arguments — furnished, conveniently, by politically tinged news sources.

As a result, said John Sides, a political scientist at George Washington University, “it’s harder for objective features of the political landscape like the economy to make a difference.”

Foreign policy has frustrated Democrats in a different way. Americans have embraced the individual policy steps Mr. Obama has taken — winding down wars in Iraq and Afghanistan, shunning ground troops in Syria. But the frightening advance of the Islamic State and its gruesome public executions have led them to conclude Mr. Obama’s overall approach is not working.