The party described "widespread" fraud, the Star-Ledger of Newark reported. The examination found 54,601 people registered in more than one county, 170,558 registered in New Jersey and at least one other state and hundreds of dead people still on the rolls.
The party cited two prominent felons who are still registered. One, developer Charles Kushner, was a major Democratic contributor before he was convicted of violating campaign financing laws, while the other, former Essex County Executive Jim Treffinger, is a Republican.
State Republican Chairman Tom Wilson said he expects the November gubernatorial election to be close.
"It astounds me that with all that happened in Florida and Ohio and Washington, that we've not been more aggressive," he said.
Wilson blamed state Attorney General Peter Harvey for failing to clean up the process.
Richard McGrath, a spokesman for the Democratic Party, said any figures coming from the state Republicans are automatically suspect.