Political entities try to create an air of inevitability for their eventual victory. You can see this at work right now in the spinning of various polls.

Manipulating the data used to create a prediction is a variation on that theme. If they could reliably do it, they would.

Influencing search traffic statistics could be done pretty low-cost, so the return wouldn't have to be that high.

It's all part of the gestalt they try to build anyway.