Strict COVID-19 policies in Democrat-led states worked, new research found. Republican-led states saw more illness.

• Democrat-led states had stricter COVID-19 responses and better health outcomes, a new study found.
• States with stricter COVID-19 rules saw 8% fewer cases, on average, than models would have predicted.
• The results show that politics shouldn't influence public-health policy, researchers say.

After nearly two years of politically charged battles over whether strict COVID-19 restrictions work – and whether they're worth the consequences – scientists awarded a point to Democratic governors this week.

A study published in the American Journal of Preventive Medicine on Monday found that COVID-19 rules in states with Democratic governors were, on average, linked to 8% fewer daily COVID-19 cases in 2020 than a mathematical model would have predicted otherwise.

Republican-led states, by contrast, had 8% more cases than the model would have expected.

To assess the strength and effectiveness of various states' COVID-19 policies, the researchers behind the study created a system they called the "Public Health Protective Policy Index." The index factored in daily COVID-19 case counts in 2020, a range policies enacted at the state level, and governors' political affiliations, then assigned quantitative values to these many factors. Then the team compared the resulting scores.

Those results showed that the public-health measures Democratic governors put in place last year were, on average, 10 percentage points more stringent than those put in place by Republican governors. And that had an observable effect on how many people got sick.

"Eight percent is not huge, but it's there. If you're wondering if policies actually matter, apparently they do," Olga Shvetsova, a political science professor at Binghamton University who led the study, told Insider.

Shvetsova said her team did not do state-specific analyses, opting instead to look at trends across multiple states. A clear political pattern emerged - one that likely would look even more dire for Republican-led states if it included data from 2021, Shvetsova added.

"What we see in Republican states is really tragic right now. They squandered their initial good fortune - badly," she said.

The link between Democratic leadership and lower COVID-19 infections does not necessarily mean that governors' actions directly drove down COVID cases, however - it's just a correlation. The new study also did not examine the relationship between political leadership and hospitalizations or deaths from the virus. Nor did it assess the degree to which states enforced governors' policies or how much residents actually complied.

What's more, a governor's politics didn't always predict the degree of strictness in a state's COVID-19 policies. In Vermont, Massachusetts, and Maryland - which have Republican governors but tend to be more liberal - GOP governors pursued more aggressive COVID-19 policies and restrictions that were more similar to Democrat-led states.

Other studies also found links between political affiliations and health outcomes

The new study builds on previous research, published in the American Journal of Preventive Medicine in July, that found a link between the political leanings of US governors and the number of COVID-19 infections and deaths by state. The researchers behind that study pointed to differences in state policies as one of the reasons Republican-led states have seen more per-capita infections since June 2020.

Up to that point, Republican-led states were recording fewer per capita COVID-19 cases, deaths, and positive tests than Democrat-led states. But from June 3, 2020 on, Republican-led states had 1.1 times more daily cases per 100,000 people, on average.

A handful of other studies have also found that overall, Democratic states had lower test-positivity rates between May and December 2020, a metric that suggests more rigorous testing and infection containment. Republican governors were also slower to issue stay-home orders and mask mandates, while Democratic leaders were both more likely to implement those rules and to leave them in place. Republican governors, meanwhile, were quicker to roll back COVID-19-related restrictions in 2020.

"Governors' political affiliation might function as an upstream progenitor of multifaceted policies that in unison impact the spread of the virus," the authors of the July study wrote. (They noted, however, that Maryland and Massachusetts bucked the trend.)

In both studies, researchers came to a similar conclusion: If politicians' priority is to keep their constituents from getting sick, they should delegate public-health policy decisions to medical and public-health professionals.

Or, as Shvetsova put it: "Politicians are creatures of their public. The public cannot be its own doctor."