A truly rational electoral activist would not vote, find a way to convincingly lie and claim that she voted, and use the extra 2 hours to make more phone calls urging others to vote.

I think this is close to the mark, but not exactly correct: a truly rational electoral activist would not vote, find a way to convincingly lie and claim that she voted, use the extra 2 hours* however she likes, and whenever the subject of voting came up in regular everyday conversation she'd urge others to get informed and vote (or just refrain from discouraging them, if she's uncomfortable/unskilled with hypocrisy).

* Two hours for voting? Whoa. Do you live in a crowded city, or very far away from the nearest station?