Of all the enemies of the happy society, fear is the greatest. Fear is the acid of trust.
The strategy of Karl Rove and his disciples had been to make their party base fearful, and forget about trying to win over the center.
In recent years they have added strategies to make it harder for everyone to vote, which hurt their opponents more than it did their supporters.
In this last cycle, I believe they gave up on trying to instill fear of things that corporate interests usually oppose, namely taxes and regulations, or that social conservatives oppose, such as abortion and gay marriage. This cycle they seemed to promote any fear at all as a way of ginning up the base. This worked against compromise and normal politics, and toward a black-and-white view of the world which their candidates would address with force.
This explains, I think, why there has been such political interest in Ebola and ISIS as things to be afraid of in this country. Notice that the promoters of these fears are not focused on the dangers of Ebola to West Africans, or of ISIS to decent people in the Middle East - where those fears are well grounded. Instead, they have promoted fear, even hysteria, about the minuscule dangers that either threat poses to Americans at home. The aim is simply fear, and anything scary will do.