Kaine has 28 votes out of 49 voters. Isn't that technically 50%?
Yes, over half of the voters have voted for Kaine, but he does not have a majority of the votes, which is currently at 81 (adding up the votes for all candidates)
What if a future poll was like this, where you could vote for two candidates:
Kaine: 7
Castro: 7
Brown: 6
Total voters: 10
The breakdown of this would be 4 voters voting for Kaine and Castro, 3 voters voting for Kaine and Brown, and 3 voters voting for Castro and Brown.
In this case, all candidates have a majority of the voters (and have passed 50%), but they also have not yet reached a majority of the votes (which is 20).
As I said in the OP, you can vote for
up to 2 candidates, so if they really liked Kaine, they could vote for only him to improve his percentage.