The graph does not provide any reason why a candidate would be trending on twitter.
We have a project that is a bit more insightful about what is actually being classified as positive and negative:
but we show a sample of the individual tweets that were classified
Here's the link to actual tweet data that is classified into positive/negative/neutral/unsure
"The vast majority of successful major crimes against property are perpetrated by individuals abusing positions of trust." -- Lawrence Dalzell