Broadly, those with power and money. Having enough money to lobby congress is one manifestation of that. Having enough money to wage large multichannel PR campaigns on the population is another. Funding think tanks, funding PACs, ownership of or influence over the major media outlets.
People with this kind of power and money form a series of formal and informal interlocking networks, and often interests align across most or all of those networks. Tax cuts for the rich and for corporations is perhaps the most obvious one. Pushing for war might be a bit less unanimous, but wars do produce near-immediate profits for the military-industrial complex and those invested in it, and potential future business opportunities for other sectors (for example if the war results in regime change, which leads to an opening of previously closed markets, the sale of state-owned businesses and assets, etc).
I think it's patently clear who is telling the voters how to vote. People usually call those by "the media" or something like that.
It is also clear who is telling the media what to say.
The one thing that is not clear at all is how much the media actually influence voters. I don't think there's as much influence as the OP was trying to convey, but well, as I said, this is not clear.
