https://www.ajpmonline.org/article/S0749-3797(21)00135-5/fulltext
This study looked at Covid rates between states led by Republican and Democratic governors over the course of the pandemic. It adjusted for population density, rurality, age demographics, health comorbidities, etc. Covid cases, death rates, and test positivity were all higher in Republican led states from the Summer through December. Testing rates were lower in Republican led states over the same period.
I tend to dislike country comparisons immensely due to all the potential confounders. State comparisons are slightly better to adjust for. But one thing that hardly is compensated for is timing. Several blue states like NY got severely hit in the March-May wave and really functionally couldn't do anything to avoid the damage besides late lockdowns because we just weren't testing for the virus.
This study gives you an idea what adjusting for timing would yield. One thing some people have been uncomfortable admitting is the partisan gap in virus mitigation behaviors. The survey data couldn't be clearer though that it unfortunately exists with Republicans more likely to hold behaviors that are more risk taking with the virus, such as lower rates of mask wearing, more likely to go to high risk places like restaurants and bars, more likely to view the virus as not a serious threat, more likely to not socially distance.
And this pattern has shown up at the policy level even more. A University of Washington study found that states led by Republican governors were significantly slower to implement a mask mandate or to implement Covid restrictions. These correlations were even stronger than the correlations for Covid death rates in the state.
