I think you need to watch some documentaries to see just how easy it is and how hard it would be to mount a real investigation. If you have a good sense of computers, like I do, you would be shocked at the electronic voting machines. It's like taking candy from a baby, and I think most of us would agree that 90% of today's political powers would not only take candy from a baby but would also punch it first.
It depends on what "documentaries" you're talking about. Most of them classify as docu-porn in my book. Created to be entertaining rather than informative. They're meant to be absorbed and perpetuated by those who've already convinced themselves of a conspiracy. Not objective at all, and very poorly researched. They make a decision first and then look for evidence to support that decision. Their research process is backwards and all evidence that runs contrary to their decision is either disgarded or minimized. I'm not saying that electronic voting machines can't be rigged, I'm just saying that the entire process would be incredibly difficult to rig. Especially the primaries. They wouldn't have to rig just a single system. They would have to rig multiple systems. Not to mention that workers at the polling stations aren't professional politicians themselves. They don't have anything to gain by helping fix the vote. So a conspiracy would have to be completely independent of their help. Then they would have to rig the votes in such a way that the results from polling thousands of people both before and after they vote wouldn't cause any raised eyebrows. This applies to pre election polls, entrance polls, and exit polls. This means that the race would have to at least be very close to begin with. Vote fraud might be able to adjust the numbers a few percentage points before people start to get suspicious. So let's say there was voter fraud against Ron Paul. In selective states they might be able to reduce him from maybe 12% down to 8%, but they almost positively wouldn't be able to knock him down to 8% from around 20%. The statistical probability of entrance/exit polls being that far off more than twice are all but zero. If he isn't consistently getting better than 20% then he doesn't stand a chance anyway and there is then no incentive to spend the time and money to rig the election against him. Again, the race would at least have to be close to begin with. He is so far out of the race in the pre-election polls, the entrance polls, the exit polls, and the actual vote, that anyone suggesting vote fraud looks like an idiot. Again, there is nothing that suggests any amount of vote fraud. You can feel free to make a case for media bias and polling bias blocking him from debates. I agree that he was unfairly blocked from the Fox debate. But truth be told he is getting an undo amount of media attention considering how low his national standing is. I've looked at somewhere around 30 different national polls and almost without exception they have him at 3-6%. Any other candidate with numbers that low would've dropped out of the race long ago. Again, I'll give you the fact that the polls are conducted in such a way as to discount his support. But any claim of huge wide-spread vote fraud is so nonsensical I don't know why I'm taking the time to respond to it.
technical matters aside, the troubling issue is the closed source code, and the lack of any rational justification for it. the machines are supposed to do 4 things only: present choices, receive input on voter selection, add inputs, and produce a total. all of these steps are trivial to code - its hard to see how these steps could include any innovation or trade secrets that would require them to be held from the public, even assuming that any such innovation should be protectable at all. these machines are paid for by the public, to perform a public duty. there is no justification for hiding how they work from the public.
Maybe I'm too reliant on what seems to be common sense. All I needed to form an opinion was to hear the CEO of Diebold pledge to deliver the Ohio vote to Bush in 2004. If American politics were portrayed in a fictional absurdist play, I don't believe it could be written to convey less integrity than the true story. Now that we all have hindsight on our preferences at the time... you have to admit that's an absurd conflict of interest between the people of The United States of America and the Diebold Corporation.