“Election officials are unanimous in their commitment to ensuring every eligible American’s right to vote, but in many places the system they oversee simply isn’t designed to handle anywhere near the number of voters that may turn out,” said Doug Chapin, director of electionline.org, a project of the Pew Center on the States. “In previous elections, the question has been, ‘Will the system work for each voter?’ But this year the real question is whether the system can handle the load of all these voters.”

Poll worker training and ballot design will be more important than ever this year. The election commission has predicted that at least two million poll workers will be needed in November, double the number in the 2004 presidential election. In New Jersey, election officials placed advertisements in newspapers asking people to sign up to work the polls. In California, election officials posted pleas on the Internet.

But many states face budget problems that make it hard to recruit poll workers. New York City election officials have said they lack the money to pay the estimated 8,000 additional poll workers needed in November. Several states have resorted to recruiting high school students.

Ms. Rodriguez said that the high level of turnover in the people who run state and local elections was also a concern. More than two-thirds of the election directors in the nation’s 50 largest counties were new to the office in 2004, and the number may be even higher now, according to Election Data Services, a Washington consulting firm that tracks voting trends.

Many voters heading to the polls in November will receive a paper ballot for the first time. The ballots are counted by optical scanners and provide a more reliable paper trail than touch-screen machines in case of a dispute or a malfunction.

A third of voters will use touch-screen machines, down from 38 percent in 2006, while about 55 percent of voters will use paper ballots read by optical-scan machines, up from 49 percent of voters in 2006, said Kimball W. Brace, president of Election Data Services.

The main issue with the paper ballots will be their unfamiliarity to voters, not the technology itself. Ideally, in fact, paper ballots could reduce lines at polling places, because election officials would not have to set up a limited number of expensive touch-screen machines in each booth. Paper ballots require only a writing surface, and far fewer optical-scan machines are needed to count them.