What is the name of the phenomenon that would make me choose A over B because I was influenced by a trend? I've looked at these 1,2,3 and I don't think they answer my question fully.

Let's say it's election time and I'm on the fence about who to vote for. I see some survey on the news and seeing party A has more vote intentions, it tends to sway my decision towards party A.

Closer to home, I see a question or answer on SE and I may feel swayed to vote +1 or -1 if there are pre-existing votes that have been cast. 

What would this phenomenon be called (if there is a name for it other than simple influence or conformity)? Also, can there be a bias for going against what the current trend is?
Bandwagon effect: 


  The bandwagon effect is a phenomenon whereby the rate of uptake of beliefs, ideas, fads and trends increases the more that they have already been adopted by others. In other words, the bandwagon effect is characterized by the probability of individual adoption increasing with respect to the proportion who have already done so. As more people come to believe in something, others also "hop on the bandwagon" regardless of the underlying evidence.


And the reason why you were not completely happy with the other questions you found (mostly on social pressure) is that there's perhaps not a single source of "bias" for the bandwagon effect. Depending on the actual phenomenon studied, social pressure or information cascades make more sense as an explanation for a given instance of the bandwagon effect. At least with respect to SE voting patterns, probably the latter makes a bit more sense. The two causes are probably not mutually exclusive.