This isn't a purely American thing, either. For quite a while, the British right's thing was Brexit. When Brexit actually happened, this kind of evaporated as a motivator, and they very visibly tried to pivot to transphobia as a primary voter motivator (it didn't really work, but it was remarkably blatant).
Previously: communists / abortion
George Bush II: terrorists / LGBTQ+ / abortion
Trump: immigrants / LGBTQ+ / educators / liberals / terrorists / gangs / etc