I am going to expand a bit on the Political Basics post I did earlier. As a recap, I gave three goals for politicians: Convince your base to support you, convince the undecided to vote for you, and convince your opponents to support your bill.
I left out one more thing - convince your opponents' base to stay home. At heart, this is the same popularity contest that you use with your own base and with undecided, but the goal is different.
The attempt to convince your base to vote for you is via fear. Fear consists of three possible actions - mudsling against your opponent (he is a bad guy, we can't let him get in), general fear of the world/other countries/natural disasters. We all can recognize a mudslinging attack (he wants to raise taxes, he cheats on his wife, he voted to praise Adolf Hitler, he beats up children, etc.), but the most common one is "he is an extremists of the wrong kind". General fear examples are: Fear of Communists, Fear of Terrorists, Fear of Running Out of Oil, Fear of Pollution, Fear of Nuclear Accidents, Fear of Bankrupt Government. Now, these fears may be true, or they may be false - that doesn't matter to the politician. The idea is to convince the base that SOMETHING MUST BE DONE (and I am the guy to do it!)
To attempt to convince your opponents base to stay home, you have 2 core options. One is to prove beyond a shadow of a doubt your mudslinging is true. This generally requires either an admittance or very good physical evidence (semen stained dress, pictures, audiotape, etc.). The other option is instead take the high ground and convince everyone their mudslinging is false. If you can effectively portray yourself as honorable and not extremists, then you can have people saying "eh, I don't care if the other guy wins." This means you have to take a middle of the road stance (see below).
The undecided generally however are not moved by fear. They don't totally believe your fear and are just as afraid that you will go too far (i.e. turning Fascist to to stop the Commies/Terrorists, giving up oil completely, stopping all chemicals, etc. etc.) Instead, to convince them, you need to demonstrate that you are not an extremists. This is often directly at odds with appealing to your own base. It will however, help you convince your opponent's base to stay home. They will however be affected by proven true mudslinging statements that your opponents base accepts.
Finally, to convince your opponents to support your bill, you need to be a moderate, or at least appear to be one.
So being an extreme helps you win your base, but also helps your opponent's base. Being a moderate, helps you defeat your opponent's base, helps your with the undecided, and helps you convince your opponent to support your bill.
But then scale pops up and knocks everything for a loop. Everything I mentioned really only applies to the average within the voting area. If an area is itself far right, than their "moderate" is actually Far Right. Similarly, in a far left district, the "moderate" is far left.
Now comes the hard part, moving from your own district to a wider stage. If you are moderate for your district, it takes a lot to realize that you are not moderate for all. Worse, as you agree with your own district, you may not even realize that yours is NOT the "real America", that in fact, you may be the wierd Extremist. This can radically shape your world view, so you don't understand the rest of the country. For example, many conservatives feel that marriage is in trouble. The weird thing is that in liberal America, marriages last longer, with fewer divorces. Marriage may be in trouble - for the conservatives. But not for the Liberals.