Also given that I quite often will nominate more than one book or second/third other books, it's possible - or some might say inevitable - that I won't vote for all of them.
There have even been times when I've nominated a book which ended up in the vote, but subsequently someone else has nominated a book that I felt was an even better choice. It happens and I certainly reserve my right to change my mind.
For example, in October I nominated The Last Werewolf by Glenn Duncan. However, when I read the description for Carmilla, I actually preferred to read that. So I didn't vote for my nomination but for Carmilla instead. You'll notice in October The Last Werewolf only got 1 vote and that was from someone who did not nominate, second or third that book.
Was that month a open voting month? No - actually it was a closed month and the voting was pretty lopsided towards Carmilla with two prospects only getting 1 vote each. Maybe in an open voting month they would both have got 0 votes each - in other words not much difference.
Picking out these "sample" months doesn't prove anything. The sample sizes are too small and the voting conducted on whim (we're not exactly electing a president).
If I fervently desire a particular book to be chosen, I will nominate it and I will vote for it and I will mention it - more than once. But I'm not always black and white about it. Sometimes there are multiple selections I'd equally like to read. Sometimes there are books I particularly don't wan't to read, and apparently sometimes I like to leap off a cliff to the music of "Charge of the Lemmings".