The man who shot the video explained the incident in a Reddit comment:
I'm the guy who shot the video, hopefully this doesn't get burried. You guys have questions, I have answers.
My wife and I went to the voting booths this morning before work. There were 4 older ladies running the show and 3 voting booths that are similar to a science fair project in how they fold up. They had an oval VOTE logo on top center and a cartridge slot on the left that the volunteers used to start your ballot.
I initially selected Obama but Romney was highlighted. I assumed it was being picky so I deselected Romney and tried Obama again, this time more carefully, and still got Romney. Being a software developer, I immediately went into troubleshoot mode. I first thought the calibration was off and tried selecting Jill Stein to actually highlight Obama. Nope. Jill Stein was selected just fine. Next I deselected her and started at the top of Romney's name and started tapping very closely together to find the 'active areas'. From the top of Romney's button down to the bottom of the black checkbox beside Obama's name was all active for Romney. From the bottom of that same checkbox to the bottom of the Obama button (basically a small white sliver) is what let me choose Obama. Stein's button was fine. All other buttons worked fine.
I asked the voters on either side of me if they had any problems and they reported they did not. I then called over a volunteer to have a look at it. She him hawed for a bit then calmly said "It's nothing to worry about, everything will be OK." and went back to what she was doing. I then recorded this video.
After the video post hit the front page of Reddit, and caused an uproar on social media, Gawker spoke to a voting machine "expert" from the Center for Democracy & Technology, who explained that the glitch was probably unintentional.
That's an obviously miscalibrated iVotronic (ES&S) voting machine... we would recommend that poll workers would recalibrate the machine and everything would be fine. Also, with some models of voting system if you place a thumb on accident while resting on the machine it can "bias" the calibration of the touchscreen up towards the errant thumb.
According to Mother Jones, who spoke to a Pennsylvania Department of State spokesman, officials have recalibrated the offending machine and put it back to work.
If you need a day's and night's worth of anxiety, check out the Washington Post's handy guide to voter irregularities across the country.