I'm a firm believer of absolutely no electronic voting machines. In-person, paper ballots, hand tallied, escorted by armed guards/trusted election officials with audited paper trails. It might cause a bit of a ruckus mentioning it here, but requiring photo ID to verify who you are before you vote should be mandatory as well.
If Israel and the USA can deploy offline-based malware to cause damage to nuclear centrifuges in Iran, what makes people think that US-unfriendly countries (or heck, even the CIA) won't try to do the exact same thing to voting machines to undermine democracy?
I wouldn't even trust open source, since I wouldn't trust election officials to keep software up to date on their voting machines, let alone know how to even update them.