Make them understand the long term implications of staying the course (in a broad sense, not just in reference to Iraq which is the context one recently hears the term in) with the 'mainstream' Republican/Democrat candidates. They must understand the economic trouble America is in, and they must understand that America WILL lose its position as the world's most prosperous nation if this continues. Economic data needs to be pointed to. For example:
America's social security obligations are staggering and far outpace the estimates of what America will be able to afford. This article explains that in 2025, there will be 2 workers paying for the benefits of each retiree, in opposed to the 3.3 workers per retiree now and the 16 workers per retiree in 1950, when social security started: Social Security's Inevitable Future
Americans' personal savings rates are in the negative and declining. This article from the federal reserve (I don't support the federal reserve setup on economic principle but I do think there are various useful articles that are published by it) shows this: Questions and Reflections on the Personal Saving Rate
American median wages, that is the wage that the largest number of Americans earn, has decreased in the last 35 years. Here are some figures to demonstrate this: wage data
Please let me know your thoughts, I can improve this if you give recommendations.