In Pennsylvania, where Sandy shut down election offices in much of the eastern half of the state, Gov. Tom Corbett extended the deadline to request an absentee ballot by two days, to Thursday at 5 p.m. But Corbett, a Republican, did not extend the deadline to return a voted absentee ballot, which is Friday.

Two days of closures also delayed processing of new registrations. In Philadelphia County, commissioners were still struggling to process 28,000 new registrations, said Ellen Kaplan of the Committee of Seventy, a non-partisan voter-advocacy group there.

Getting all the polls open in all 67 counties on Election Day may be a problem as well. About 1.2 million customers in Pennsylvania lost power in the storm, and utilities warned that restoration might be more than a week away.

Corbett said Tuesday he had directed his secretary of state to survey all counties and give him a report, which he said could help make sure all polls had power for their voting machines.