Florida's election fiasco in 2000 prompted many states to adopt electronic touch-screen voting systems, but after a spate of malfunctions and meltdowns in 2004 and 2006, paper ballots are making a big comeback.

At least 55 percent of American voters this fall will mark their choice for president on paper ballots that will then be read and tabulated by optical scanning devices - nearly double the percentage in 2000, according to Virginia-based Election Data Services, a consulting firm that has been tracking voting technology since 1980.

Electronic touch-screen voting will decline for the first time in eight years, and punchcard ballots, once used by nearly one-third of the electorate, will be used in only 12 counties in Idaho.

In the trend toward paper-backed systems, the hulking old mechanical lever machines, introduced more than a century ago, are also headed for extinction. Only the state of New York still uses them.

Massachusetts and the other five New England states use paper-based voting systems, mainly optical scanners but also hand-counted paper ballots in some areas.

With change, however, comes potential for error. New technology and the likelihood of heavy turnout in November will put added strain on Election Day workers, a part-time army of low-paid employees, many of them retirees.

"Since 2000, upwards of 70 to 75 percent of the nation has changed voting equipment," said Kimball W. Brace, president of Election Data Services. "Every time you make a change, it has the potential of causing problems . . . Inevitably, the biggest problems occur the first time you use new equipment."

Since the Florida recount tipped the Electoral College to George W. Bush in 2000, that state has changed its voting methods twice. First it dumped punch cards after the embarrassment of hanging chads and dimpled ballots eight years ago, which caused votes to go uncounted and created doubt about many voters' choices.

After a series of highly publicized errors with computerized touch-screen equipment in 2004 and 2006 in some of the state's most populous counties, Governor Charlie Crist and the Legislature last year mandated optically scanned paper ballots in all 66 counties. The final blow came in 2006 when touch-screen machines in Sarasota County recorded an anomalous 17,846 "undervotes," or blanks, a rate of almost 15 percent, in a congressional election decided by 369 votes. State and federal reviews failed to explain the phenomenon.

"We cannot afford to have any more issues at the polls," said Kurt S. Browning, who was appointed secretary of state by Crist after the Sarasota problem. "We know that regardless of what we do, we're going to be under a great deal of scrutiny, which is OK. Our supervisors across the state and their staffs are working hard; they're committed to conducting a good election."

Iowa and New Mexico have also abandoned touch screens in favor of paper ballot systems, and states such as California will not certify a touch-screen system unless it creates a paper backup that meets rigorous audit standards. North Carolina mandated paper-backed systems after a series of touch-screen malfunctions in 2004, including the disappearance of about 4,000 votes in Carteret County. Most of the Tar Heel State's 100 counties now use optical-scan paper ballots, according to Johnnie McLean, deputy director of the state board of elections, but about one-fourth use touch-screen machines backed by a paper record known as an audit log.

States also utilize some form of specialized technology at each polling place to help persons with various disabilities vote privately and independently, in compliance with federal law.

In 2004, Ohio became the new Florida, plagued by irregularities and charges of partisanship against the Republican secretary of state at the time, J. Kenneth Blackwell, a cochairman of the Bush campaign in a state the president carried by fewer than 119,000 votes out of 5.6 million cast. Since 2004, when many Ohio counties still used punchcard ballots, the state has moved to other technologies - 35 counties use optical-scan paper ballots and 53 counties employ touch screens backed by what is known as a voter-verified paper audit trail.

Jennifer Brunner, a Democrat, succeeded Blackwell in 2006, and initiated a $1.8 million study that identified problems with the state's voting system. Partisanship, however, still permeates the politics of election management in the Buckeye State. The Republican-controlled state Legislature and Brunner have been at odds over voting technology and funding issues. In December, Brunner broke a party-line tie vote of the Cuyahoga County Board of Elections after Republican members opposed her move to discard the county's perennially troubled touch screen machines in favor of optical scan paper ballots.

Brunner said Ohio is instituting standardized procedures and training methods, and the March 4 presidential primary went off without major problems. In November, she predicted: "I think you're going to look at Ohio and see a smooth election run by officials who were prepared."

Even the best voting system can be undermined by human error. Last fall, electionline.org, a project of the Pew Charitable Trusts, issued a report that described poll workers as "a massive one-day workforce" of about 2 million for each federal election, typically working more than 12 hours at minimum wage or slightly more. But the report found that "training, abilities, and compensation of that army is far from uniform."

In many cases, they must deal with changing voting technologies and registered voter lists that are flawed, which can result in the issuance of provisional ballots. At least seven states are not yet fully in compliance with a requirement of the Help America Vote Act of 2002 that every state have a centralized database with information about all registered voters. The central lists are a resource for poll workers to resolve questions about voter eligibility on Election Day.

Rosemary E. Rodriguez, chairwoman of the federal Election Assistance Commission, said poll staffing is another concern because of the likelihood that high voter turnout in November will strain the system. The commission, created by the 2002 voting act after the Florida recount problems, is an information clearinghouse and assists states in meeting the law's requirements. Last week the commission announced grants of $750,000 to 27 colleges and nonprofit groups in 18 states to recruit about 8,800 student poll workers for Election Day.

Brace, a consultant who specializes in election administration and redistricting issues, said: "It continues to be difficult to find people to work at the polls." The typical election-day poll worker, he said, is older, likely to be unfamiliar with technology, and lives in a sparsely populated area.

Of 10,072 jurisdictions, mostly counties, that conduct elections, most - about 7,000 - have fewer than 10,000 registered voters, Brace said, and only 320 have more than 100,000. "Usually, it's a county clerk who also takes care of the taxes and who knows what else," he said.

The flaws are always magnified in the case of recounts, none more so than in Florida eight years ago.

Doug Chapin, director of Pew Charitable Trusts' electionline.org, said one benefit has been increased public interest in what he called "the nuts and bolts of elections." It's also the reason, he said, that the silent prayer of election officials everywhere is: "Dear Lord, let it be a landslide."