In a primary faceoff between two veteran Democratic incumbents, voters in Ohio delivered a victory to Representative Marcy Kaptur, a progressive from Toledo, over Representative Dennis J. Kucinich, leaving him without a seat in Congress for the first time in 16 years.

Mr. Kucinich conceded just past midnight Wednesday. With nearly 85 percent of the vote counted, Ms. Kaptur led Mr. Kucinich, her colleague and frequent ally in the House, by about 24 points in the race to represent Ohio’s recently redrawn Ninth Congressional District.

The outcome was largely expected. Mr. Kucinich, an antiwar populist from Cleveland who has run for president twice, lost his district when state lawmakers redrew the electoral map after Ohio, whose population has been dwindling, lost two Congressional seats last year. The new district — a skinny strip of land that covers parts of five counties from Cleveland to Toledo — contained more of Ms. Kaptur’s old territory than Mr. Kucinich’s, and Mr. Kucinich had been struggling to win over voters in areas beyond his traditional stronghold of Cleveland.

It is not clear whether Mr. Kucinich will try to run for public office somewhere else. After his district was eliminated last year, he visited Washington State to explore his options, though his spokesman, Andy Juniewicz, said that Mr. Kucinich had said he “never had any intention of leaving Cleveland.”