It's Not the People Who Vote That Count, It's the Machines That Count the Votes.
Many districts have been pushing hard for electronic voting machines. People believe that electronic devices are going to be more reliable for elections than any mechanical system could be. Machines that are used in the voting process are mechanically simple and thus it's fairly easy to predict what kind of failures you'll run into unlike complex electronic devices:
Tests on an electronic voting machine that recorded shockingly high numbers of extra votes in the 2010 election show that overheating may have caused upwards of 30 percent of the votes in a South Bronx voting precinct to go uncounted.
WNYC first reported on the issue in December 2011, when it was found that tens of thousands of votes in the 2010 elections went uncounted because electronic voting machines counted more than one vote in a race.
A review by the state Board of Election and the electronic voting machines’ manufacturer ES&S found that these "over votes," as they’re called, were due to a machine error. In the report issued by ES&S, when the machine used in the South Bronx overheated, ballots run during a test began coming back with errors.
“After lunch [when the machine was idle for about an hour] almost every ballot was read incorrectly, in all orientations, even ballots that had read correctly just before lunch,” the ES&S report said.
Electronics are finicky and generally much more prone to unpredictable failures than mechanical devices. Minor variances in temperature, moisture, and electrical conditions can cause electronics to fail in strange and difficult to predict ways. Combine this with the fact computer software is almost impossible to write well and you have a perfect storm for massive electron fraud.