What's to stop someone from making a ton of mining nodes as an attack method? My understanding is that if two miners make a block by completing a hash at the same time, it is then up to the miners to decide which is going to be 'accepted' by vote of which block reaches 51% of the votes first.  

What's to stop someone from making a ton of nodes just so that they can get an advantage if this situation arises for himself? (Another node finished a block at about the same time as me, so I unleash my army of nodes to all vote for the block that I made)
When two blocks are found at the same height, only one can ultimately become part of the chain with the most total work. Miners do 'vote' which of the blocks to accept, however this is not by casting a ballot, but by producing a succeeding block and thus making one of the two chains longer than the other. Miners thus vote with their hashpower by trying to extend one or the other chain-tip.

Thus the "attack" you describe is impractical: if miners only used their expensive mining hardware solely to decide chain splits, they'd be losing out on a lot of revenue. Instead, they mine all the time to find as many blocks as possible.

Also see:


Why doesn't the same miner always win?
How much would it cost to execute a 51% attack?