Mr. Kasich added insult to Mr. FitzGerald’s injury recently by refusing to debate him, the first time in decades Ohio’s opponents for governor are not meeting as equals on a stage. After “the other side imploded,” said a spokeswoman for the Kasich campaign, Connie Wehrkamp, “we decided it was better to move on.”

Just five weeks before Election Day, Ohio Democrats have descended into recriminations, with many angry and frustrated that the state party did not do a better job vetting the little-known Mr. FitzGerald, handing him the nomination without a primary that could have aired his past. “It was incredibly foolish; Ed had never really been tested,” said Greg Haas, a Democratic operative in Columbus.

The party chairman, Chris Redfern, pointed a finger at Mr. FitzGerald himself. “I’ve never met a former F.B.I. agent who doesn’t have a driver’s license,” he said. “It’s akin to saying, ‘Damn, I should have my umbrella’ after it rains.”

Mr. Redfern, a State House member, said no other major Democrats stepped up to run in a primary. As for vetting Mr. FitzGerald, he blamed an outside group that the campaign hired to research the candidate’s vulnerabilities. Mr. Redfern said he would not hire the company “to clean out my bird cage.”

An across-the-board loss by Democrats in November would mean that heading into 2016 Republicans would control the agenda in the Legislature, and its priorities dominate news media coverage. It would also mean Democrats have a shallow bench for future races for governor if its rising stars, including Ms. Turner and Connie Pillich, an Air Force veteran running for state treasurer, are deprived of understudy roles in statewide offices.

“From cycle to cycle you try to keep your base energized,” said Mark R. Weaver, a Republican consultant in Columbus. “The Democrats won’t be able to do that. They’ll have to spend even more resources to re-engage their base come 2016.”

Many Democrats denied that they would be at a disadvantage in the next presidential cycle. They pointed to the bounce-back of activists after a Republican wave four years ago, when Democratic volunteers staffed more than 150 field offices in President Obama’s re-election race, a surge that played a decisive role in turning out the vote that gave the state to the president.