HILLARY CLINTON has vowed not to raise taxes on the middle class.

It’s a pledge that has worked well for others on the campaign trail before her, a resonant assurance to voters who saw themselves as middle class or aspired to be. But it’s a bad promise.

Mrs. Clinton is using a definition of middle class that has long been popular among Democratic policy makers, from her husband to Barack Obama when he was a candidate: any household that makes $250,000 or less a year. Yet this definition is completely out of touch with reality. It also boxes her in.

The most recent Census Bureau data showed that median household income — what people in the exact middle of the American spectrum earn — is $53,657.

Those families who make $250,000 a year, on the other hand, belong to an elite group: Americans who earn enough to be in the highest 5 percent of the income distribution. That top stratum captures anyone who makes $206,568 or more — not everyone in the so-called middle class that Mrs. Clinton says she is dedicated to protecting, but too large a chunk of it.