WASHINGTON — In the aftermath of Democrats’ demoralizing election defeat, Representative Nancy Pelosi’s bid to return as minority leader has been transformed into a larger debate about what has gone wrong with a party that eight years ago controlled Congress and the White House.

Ms. Pelosi, a 76-year-old San Francisco progressive, is expected to easily win re-election when her colleagues vote on Wednesday. But she has become a stand-in for complaints that Democrats have failed to offer a compelling, broad-based economic message to the working-class voters in the Midwest and South who helped them capture the House 10 years ago and made Ms. Pelosi the first woman speaker.

Representative Tim Ryan, who represents a blue-collar district in northeastern Ohio, has mounted an unexpected challenge to Ms. Pelosi and given voice to the message that House Democrats must broaden their appeal beyond the three liberal states — California, Massachusetts and New York — that now account for a third of their members.

Mr. Ryan argues that his party can only rebuild if it re-establishes itself as the party of the working class.