Ever since Al Gore claimed the 2000 election was "stolen" from him, liberals have made the claim that the large corporations that make voting machines can't be trusted to provide elections without cheating. Here are the reasons why this claim is false:
The cheating could happen only once.
Once cheating is uncovered, nobody would ever again trust machines made by that company. The cheating by that company could not happen again, because the machines made by that company would never again be used in any elections.
The cheating is likely to be discovered.
There are so many interrelated pieces of data in an election that it would be very hard to significantly change the outcome of one race without causing statistical anomalies. Likewise, it would be hard for the person entering the election information into the machine to cheat in such a way that it would not cause statistical anomalies.
In addition, a machine suspected of having been used to cheat can be impounded and examined by independent experts. There would be no way to hide clandestine software from this examination.
Most of these companies are trusted providers of security for banks, ATMs, money transfers, and other sensitive areas.
Credibility in these markets would be destroyed by any revelation of a company doing any cheating in an election.
Any company involved in election fraud would be immediately ruined.
Any security company found to be involved in election fraud would instantly lose ALL of its customers. Even counting any money it receives as bribes for perpetrating the fraud, any company involved in election fraud would go bankrupt very quickly. Stockholders would dump any stock it offered, and nobody would do business with it or trust it.
It's not worth the risk.
No company in competent hands would destroy itself for a one-time windfall of money.
There are several effects that make it look like someone is cheating. Here are some of the causes:
The public opinion polls are biased toward liberal candidates.
This is not because the polls are deliberately favoring liberal candidates. The trouble is in their data collection methods. They collect data mainly in large cities, to save money. Unfortunately, more city dwellers vote liberal.
The Plurality Voting System is biased.
The real problem is that third party candidates siphon votes away from the mainstream candidate with a similar platform. This can often hand the election to the other mainstream party. In 2000, Al Gore lost the election, because Ralph Nader took away enough votes to let George Bush win the electoral votes of Florida and New Hampshire.
There are other cheating factors at work.
Election Cheats have plenty of other methods they use to steal votes. They don't have to rig the machines. They usually get by with fooling the people.
Liberals tend to believe that most people think as they think.
Because they believe that they have a vast majority of people who think as they do, they can't believe it when the other candidate wins. The only reason they can think of for losing the election is that someone cheated. They can't believe that the majority of the voters voted for the other candidate. Some of them even went so far as to try to use the fact that their candidate lost as "proof" that the other side cheated.