In some cases Tuesday, problems with optical scan machines seemed to be connected to rain. Voters brought moisture into the polling places and the optical scan machines jammed because of damp paper, he said. In other places, voters raised questions because their ballots were put in boxes waiting to be scanned instead of scanned immediately, he said.

Those problems may have been predictable, but a lot of the problems center around training of poll workers, many of whom aren't familiar with the technology, Spafford said. More extensive training will cost money.

In other cases, any problems with voting machinery were compounded by record voter turnouts. Several states have moved to allow early voting, and other states may want to consider it, Spafford said.

In the rush to adopt new voting technology following problems with paper ballots in the 2000 elections, many states adopted unproven technology, he added. While most states that purchased touch-screen voting machines have since moved to include printouts with those machines, other states have switched to optical scan machines.

Three states, Maryland, Tennessee and Colorado, will move to some kind of paper backup in coming elections. But that still leaves 15 states where touch-screen machines would be used without paper backups, and replacing or reconfiguring those machines would cost millions of dollars.