I think there's research saying that happier people tend to be more politically conservative, no?
I've seen that before, but I think it's self-reported which makes things tricky; Conservatives are significantly less likely to say if they're unhappy, struggling mentally, ect.
This is literally what it means to be happy. To be
resilient to negative feelings and external stressors. A conservative worldview is correlated with all sorts of cognitive behaviors (i.e., increased religiosity, more moral clarity, better sense of self-empowerment, etc.) that are demonstrated to improve mental well-being.
The idea that Republican messaging is so overwhelmingly negative that conservatives must be angry, scared, depressed is a Democrat fantasy. And even if it was true, are liberal messages about climate change or the future health of U.S. democracy very positive?