Customers pump gasoline into their cars at a gas station in the Bronx, New York, where gas prices rose to over $3 per gallon in June.

From a distance, the 2018 midterm election campaign poses a mystery: With the economy so good, why are prospects for President Donald Trump's party so bad?

But a closer look solves it. "The economy" may be roaring, but for most voters their economy is not.

The difference between those two things reflects the income inequality that has defined America's modern economy. The positive news Wall Street savors — robust corporate profits, rising stock prices, surging output growth — deliver the greatest rewards to a relatively modest share of more affluent Americans.

The rest don't feel it all that much.

"Fifty-one percent of the electorate lives paycheck-to-paycheck," explains David Winston, a strategist for GOP leaders battling to save their House majority. "Their issues are wages and the cost of living. Ultimately for those folks, the question is, are those paycheck-to-paycheck dynamics getting better?"

"When you talk about 'the economy' writ large, that is an abstraction for people," adds Geoff Garin, a pollster assisting Democratic efforts to recapture the Senate. "When you talk about getting to the end of the month and being able to pay your bills and set some money aside, that's not an abstraction."