The slowdown began in February 2007 when the commission took over the certification process that was previously performed by a volunteer program operated by the National Association of State Election Directors. Until then, the association had arranged for private testing labs to scrutinize the machines, using standards set in 1990 and 2002 by the Federal Election Commission. That process was widely criticized as being inconsistent and rife with conflicts of interest.

“The problem is that the pace of innovation is outstripping the pace of regulation,” said Doug Chapin, director of the Web site set up by Pew Center on the States, electionline.org. “Federal certification is intended to help election officials manage voting technology, but right now it’s getting in the way instead.”

Since the commission took over the certification process, no new equipment or software has been certified.

Advocates for better election systems say one reason for the delay is that the machines are fraught with problems that should have been detected earlier, giving manufacturers more time to make improvements. Had there been stronger standards before the commission took over, they say, the current level of scrutiny would not be necessary.

“The E.A.C., to its credit, has decided to dig their collective heels in and insist that the software and hardware be rigorously tested by professional testing labs,” said Warren Stewart, a technology expert with Vote Trust USA, a voting rights watchdog group.

Either way, said Chris Nelson, the secretary of state in South Dakota, which requires federal certification of voting-machine changes, he is tired of waiting.

In 2006 the ballot-marking devices used by disabled voters incorrectly marked 50 to 100 ballots, Mr. Nelson said. The machine maker says it has fixed the problem but the state cannot install the fix without certification, said Mr. Nelson, who added that he had also not decided how to proceed.