By Laura Smith-Spark
Critics claim electronic voting machines are vulnerable to hacking
Millions of people will expect to hear the US mid-term results within hours of the close of polling. But as problems are reported with new voting technology, could their wait be prolonged?
Across the US, dozens of states have used electronic voting machines - many for the first time.
The devices have been brought in to replace the old-fashioned lever and punch-card machines - the latter at the centre of the "hanging chad" debacle in Florida in the 2000 presidential election.
Keen to prevent a repeat of such embarrassment, Congress in 2002 passed the federal Help America Vote Act, calling on states to update their equipment in time for the 2006 elections.
However even ahead of the polls, many questioned whether the new systems would bring all kinds of problems of their own - potentially resulting in recounts, court challenges and a painful wait for final results.
Voters have encountered two main types of new technology at the polls.
Paperless touch-screen machines are in place in 33 states. Elsewhere, voters have been asked to fill out a paper ballot which is then read by an optical scanner and tallied automatically.
Concerns have focused on the touch-screen machines, with local officials worried about both their accuracy and the lack of a paper trail to verify the votes cast.
Critics say they are vulnerable to computer failure and deliberate hacking, laying results open to claims of fraud; lawsuits have been filed in several states seeking to bar their use.
Maryland's Republican Governor Robert Ehrlich has been one of the most high-profile sceptics, after his state's primary vote in September was plagued by computer glitches.
Some polling stations opened late because workers had not been given cards needed to work the voting machines; in others, computers crashed or failed to register voters' party affiliation correctly.
The governor, who is himself up for re-election, said he had opted to cast his mid-term vote by absentee ballot through the post - and he has urged fellow voters in the state to do the same.
"When in doubt, go paper, go low-tech," he said.
Change of tack
Officials in New Mexico and Connecticut have in the past year dropped plans to use touch-screen machines and opted for paper ballots with optical scanners instead.
No state wants a repeat of Florida's hanging chad debacle in 2000
"I didn't want my state to continue being an embarrassment like Ohio and Florida every four years," New Mexico's Governor Bill Richardson told the New York Times.
Few will have been reassured by a study this summer by Steve Freeman, a visiting professor at the University of Pennsylvania, which suggested it was easier to rig an electronic voting machine than a Las Vegas slot machine.
And only last month, a supplier of US voting machines, Smartmatic - the parent company of Seqouia Voting Systems - agreed to an inquiry following suggestions it has ties to Venezuela's anti-US President Hugo Chavez. The firm denies the claims.
Against this backdrop, a survey by Gallup last month showed that only one in four Americans is "very confident" his or her vote will be accurately counted.
Both Republican and Democratic Parties have employed a small army of poll watchers and lawyers to monitor voting, particularly where races are close.
Electoral rights campaign groups have also raised concerns over electronic machines and changes in voter ID and registration rules ahead of polling.
Some problems have been "exacerbated" by the new measures, a joint report by the Century Foundation, Common Cause and the Leadership Conference on Civil Rights warns.
Several of the states it highlights are on the list of key battleground races for House and Senate seats - Missouri, Pennsylvania, Ohio and Michigan among them.
The report's main author, Tova Wang, told the BBC News website there was "no doubt there will be places where machines malfunction" - and that this was likely to raise voters' suspicions that the machinery had been manipulated.
Problems could mean voters are again kept waiting in long queues
However, she said, problems were far more likely to result from human error.
Many states have installed the new technology within the past year and have struggled to train up poll workers - many of whom are older people less used to new technology - in time, Ms Wang said.
She fears any problems could lead to long lines of voters, as seen in Ohio in 2004, with the result that some people miss out on casting their vote. Others may have to revert to paper ballots, leading to slower counting.
The high number of absentee ballots cast by people suspicious of the new technology could also delay the count in some states.
"The question I ask is whether officials have a back-up plan in case things don't go perfectly... or are they just keeping their fingers crossed?" said Ms Wang.
"In those places which are very close, you can count on seeing some controversy and possible litigation."