Economics and politics
It was famously said about Bill Clinton's run for the White House, "It's the economy stupid." And surely no single force drives the short to medium term swings of American politics like the economy. But that is not the reason I think every political science student should be required to take at least an introduction to economics class. Instead, economics classes teach you a different way of looking at the world, and why things work the way they do.
One of the most basic concepts in economics is that of the positive and negative externality. A positive externality is when there is a benefit from a good that is realized by someone other than the one purchasing/using it. Think about that in political terms. As a single guy with no kids why should I pay taxes for schools? Because I realize a benefit from teaching the child who is actually using that product (an education), from keeping them out of trouble in the short-term to making sure they have a job to pay my social security in the long-term.
Why impose environmental regulations on business? Because pollution is a negative externality. The people producing it don't have to personally experience all the harm from the cancer and other diseases their pollution causes. Those who pray to the absolute dogma that free markets can do no wrong need to get past the first month of a high school economics class and then start talking. Economics says that products with positive externalities tend to be under produced and those with negative over produced without intervention. In other words without government you would end up with too many uneducated kids with asthma.
But these same lessons apply to campaigns too. Why are negative campaign ads overused? Because Candidate A running one does not bare all the cost of the harm done to the general public attitude towards politics. It is a negative externality. Why are political campaigns slow to innovate? Because they are by definition fly-by-night organizations that shut down as soon as they open. So why spend a lot of resources on "R&D" when the only ones who will realize the benefits of that knowledge are future campaigns. It is a positive externality.