Agenda Setting is a bane of any media. It's often interpreted by readers merely as the choice of stories to cover, much as the agenda of a meeting is often controlled by the chairperson with some input from the other participants. I've even heard arguments that participants, in this case readers of the newspaper, collude in the agenda by only buying papers that talk of airplane crashes and murders. But a deeper aspect of agenda setting is the placement of stories and facts within the stories and writing articles that appear to include all sides of an issue by mentioning them, but really only focus on two sides, a point-counterpoint or contrast and compare of the most easily delineated sides.
I'm a member of the Libertarian Party, and I also voted for Greens last election. As a Baha'i, I am not supposed to engage in politics. I infer this means not personally engaging in negative political behavior such as backbiting and making false promises, and not publicly entering politics as a church to avoid the problems associated with governing popes and ayatollahs. But my religion also says that I have to support a just government, which in America means I must vote which means dealing with political parties.
Mark Hanson said there are "two main parties in this country." Pete Salg agreed and said they have both been "hijacked by fanatics." But their joint solution was to join one of those hijacked parties to counter the fanatics.
Because voters act as if there are only two parties, then we are setting the agenda for an either-or split that will always tend to widen because fanatics, single issue voters, and extremists can only choose one or the other, and these people often have the time and energy to devote an inordinate amount of effort to politics.
Another effect of this two party system is that people immediately assume officials are voting for their party. I'm sure there are some Democratic Senators conscientiously thinking that overturning a public election is more serious than getting rid of an appointed judge, and there are some Republican Senators who sincerely believe that lying under oath is reprehensible enough to require removal of a sitting President. However, they are branded as politicos toeing the company line.
Mark Hanson did make a good point about voters having more say from within a party than as an independent. If we had several viable parties of relatively equal strength corresponding to the relatively equal strengths of the electorate's multiplicity of viewpoints, the fanatics would be in their own smaller parties and the larger parties would be agreeing on some issues but not others. Currently, it appears as if the Democrats and Republicans always disagree about stuff. There's the classic "Fix Social Security" either with more money or less benefits. The reality is that they both agree government can solve our problems.
If you believe government is causing some of our problems, then the solution is not to join one of the colluding parties. The solution is to create more parties for a wider agenda.