- Convince undecided/opponents to vote for them.
- Convince their base to support them (both money and to show for the vote).
- Convince your opponent to vote for your bill.
To do these three simple things, they have three simple mechanism.
To convince undecided you have to make plausible and moving arguments. They don't have to be true or logical, just plausible. However, what is plausible over the short term is not always plausible over the long term. For example, the Obama's plan to close Guantánamo was plausible when he said it, but not now. Similarly, many of the McCain's claims of Obama's military naivety was more plausible but it isn't going to be made this year. They also have to be moving. Discussing dry facts does nothing,
Note, plausible and moving statements are what the main stream (both liberal and moderate) media respect. They are considered 'high brow' and important by the movers and shakers. It is also what they expect in 'ivory towers'. Your opponents watch these carefully, they need to be countered.
Next is the appeal to the base. Your goal here is FEAR. Plausible is a detriment here. This is why you have idiots claiming that Bush knew about/participated in 9/11 and that Obama is not a citizen. It is the speciality of people like Rush L., Glenn B., S. Colbert, and J. Stewart These people already believe in you, your goal is to motivate them to give cash and time, not to convince them. More importantly, when the fears fail to manifest, you can say "With your help, we STOPPED them. Give more please." The main stream media despises appeals to the base, because the less truth in them, the more effective. I should state that I am proud of the fact that Colbert and Stewart recognise that what they say is implausible. But the function they serve is pretty much the same as Rush and Glenn - to talk about ridiculous things, motivating the base.
Finally to convince your opponents to vote for your bill is very difficult. There are really only two techniques. One is compromise - give up part of what you want to get the rest. The other is to ask for more than you want and pretend to compromise by giving up your 'extra' stuff. Note, often you choose a spokesman that is 'out of the loop' and does not know if you are actually compromising as opposed to pretending to compromise.